Short answer: At 100,000 monthly active users in 2026, Better Auth costs $0 in license fees, Clerk Pro costs about $1,025 a month, and Auth0's B2C Essentials rate of roughly $0.07 per MAU extends to about $7,000 a month. Clerk is the best value up to 50,000 retained users, where it costs $0 on Free or $25 on Pro and gives you the best prebuilt Next.js login UI. Better Auth wins on price above that if your team can build and run its own sign-in flows, and Auth0 is worth its premium only when customers require SAML, LDAP, or Okta-approved procurement.
All three vendors price authentication differently, so the comparison that matters is the bill at a specific user count. Clerk bills monthly retained users. Auth0 bills monthly active users from the first paid user. Better Auth has no bill at all: it is an MIT-licensed TypeScript library that runs inside your app and stores users in your own database, so its cost shows up in engineering time and your email provider's invoice.
Prices are list rates from each vendor's pricing page as of October 2026. They match the figures in our Clerk vs Auth0 vs Supabase Auth review and our Next.js Postgres and auth cost breakdown, so the numbers agree across the site.
Clerk vs Auth0 vs Better Auth at a glance
| Option | Best for | Model | Free tier | Entry paid price | Key trade-off |
|---|---|---|---|---|---|
| Clerk | React and Next.js teams that want login, organizations, and invitations working this week | Hosted service with embedded React components | 50,000 monthly retained users (MRU) per app | Pro, $25/month with 50,000 MRU included | $0.02 per retained user from 50,001 to 100,000 |
| Auth0 (B2C Essentials) | Enterprise identity: SAML, LDAP, custom databases, Okta-aligned procurement | Hosted service with Universal Login redirect | 25,000 MAU, limited features | $35/month for 500 MAU | About $0.07 per MAU from the first paid user |
| Better Auth | Teams that want users in their own Postgres and no per-user fee | Open-source library inside your app | Unlimited (MIT license) | None; you pay for email and database | You build and maintain the sign-in experience |
Monthly cost at 10K, 25K, 50K, 75K, and 100K MAUs
Paid tiers are shown because production apps tend to need them. Free-tier figures follow in parentheses where they apply.
| Monthly users | Clerk | Auth0 B2C Essentials | Better Auth |
|---|---|---|---|
| 10,000 | $25 Pro ($0 on Free) | $700 ($0 on Free, limited features) | $0 plus email |
| 25,000 | $25 Pro ($0 on Free) | About $1,750 ($0 on Free, limited features) | $0 plus email |
| 50,000 | $25 Pro ($0 on Free) | $3,500 | $0 plus email |
| 75,000 | About $525 ($25 + 25,000 × $0.02) | About $5,250 (extrapolated) | $0 plus email |
| 100,000 | About $1,025 ($25 + 50,000 × $0.02) | About $7,000 (extrapolated; expect an Enterprise quote) | $0 plus email |
The Auth0 figures at 25,000, 75,000, and 100,000 extend the roughly $0.07 per MAU rate behind its published $700 and $3,500 price points. Above 50,000 users Auth0 generally moves customers onto a negotiated Enterprise contract, so treat those numbers as the opening position for that conversation, not a quote.
Clerk's numbers count retained users, not every sign-in. A user counts only if they come back at least a day after signing up, so a launch-day spike of sign-ups who never return costs nothing. That flatters Clerk early and stops mattering once you have a retained base. Auth0 counts everyone who authenticates in the month.
What each extra user costs you
| Provider | Billing unit | Marginal cost per user, 10K to 50K | Marginal cost per user, 50K to 100K |
|---|---|---|---|
| Clerk Pro | Monthly retained user | $0 (included in $25) | $0.02 |
| Auth0 B2C Essentials | Monthly active user | About $0.07 | About $0.07, or a negotiated rate |
| Better Auth | None | $0 license; email and database only | $0 license; email and database only |
Auth0's per-user rate is 3.5 times Clerk's overage rate. Clerk's own curve is flat to 50,000 retained users and then steepens, which is why the 50,000 mark is where most teams on Clerk start asking whether to switch.
The real cost of Better Auth's $0
Better Auth is free the way a self-hosted mail server is free. The license costs nothing. What you take on is the work Clerk charges $1,025 a month to do at 100,000 users: sign-in and sign-up screens, verification and password-reset emails through your own provider, rate limits on the reset endpoint, and on-call ownership when the session table misbehaves.
The trade is easy to reason about. If your team can spend a few days building login flows and keep an eye on them afterwards, Better Auth saves about $500 a month at 75,000 retained users and about $1,000 a month at 100,000 compared with Clerk, and several thousand a month compared with Auth0. If engineering time is your scarcest resource and you are below 50,000 users, Clerk costs $25 or less and that saving does not exist yet.
Two other points favor Better Auth beyond price. Users sit in your own Postgres tables, where joining against them is ordinary SQL, and moving hosts means moving a database dump. The Auth.js project (formerly NextAuth) is now maintained by the Better Auth team, which settled the open-source question for most new Next.js projects. If you run Better Auth on a scale-to-zero database such as Neon, turn on its session cookie cache so most requests skip the database lookup; our Postgres and auth cost breakdown shows the configuration.
Where Clerk and Auth0 still earn their price
Clerk scored 9.0/10 in our auth review against Auth0's 7.5, and we rate Better Auth 8.6. In our tests Clerk integrated in about a day against about three for Auth0, and signed users in faster (340ms against 410ms P95). Its organizations, invitations, and roles are built into its components, work you would otherwise build and maintain yourself on Better Auth. For a B2B SaaS under 50,000 retained users, that is the best deal of the three.
Auth0 wins a narrower but real case. SAML, LDAP, and custom database connections are first-class, Actions run your Node.js code inside the login pipeline, and Okta ownership carries weight in vendor-risk reviews. If an enterprise customer's security team hands you a checklist, Auth0 may be the cheapest way to pass it even at $0.07 a user.
Where each option fits (and where it does not)
| Option | Fits | Does not fit |
|---|---|---|
| Clerk | React and Next.js apps under 50,000 retained users; B2B SaaS that needs organizations and invitations now; teams with no time to build login UI | Consumer apps heading past 50,000 retained users on a tight budget; teams that need self-hosting or users in their own database |
| Auth0 | Enterprise customers who bring SAML or LDAP; in-pipeline custom code via Actions; Okta-approved procurement | Consumer or early-stage SaaS at any volume we priced; small teams that do not want a configuration surface with hundreds of settings |
| Better Auth | Apps expecting 50,000 to 100,000+ users with an engineer who can own auth; teams that want users in their own Postgres | Teams with no capacity to build and maintain sign-in screens, email delivery, and rate limiting; buyers who need a vendor SLA for identity |
None of these is our product. Some reviews on this site include affiliate links, and those relationships do not influence ratings or recommendations. The ratings above reflect developer experience and features; the price gap at 100,000 users is what moves the recommendation from Clerk to Better Auth for cost-sensitive apps.
Our pick by user count
Under 50,000 retained users: Clerk, on Free or the $25 Pro plan. Expecting 100,000 users within a year: Better Auth, chosen before launch so there is nothing to migrate. Selling to enterprises that require SAML or LDAP: Auth0, or Clerk's SAML SSO on paid plans if the checklist allows it. If you already run Supabase, compare Supabase Auth, which includes 100,000 MAUs in the $25 Pro plan; see our Clerk vs Auth0 vs Supabase Auth review.
Frequently asked questions
How much do Clerk, Auth0, and Better Auth cost at 100,000 MAUs?
At October 2026 list prices, Better Auth costs $0 because it is an open-source library that stores users in your own database. Clerk Pro costs about $1,025 a month: $25 plus $0.02 for each retained user from 50,001 to 100,000. Auth0 B2C Essentials runs about $0.07 per MAU, which extends to roughly $7,000 a month, and at that volume Auth0 usually quotes an Enterprise contract instead.
How much do Clerk, Auth0, and Better Auth cost at 10,000 MAUs?
Clerk costs $0 on its Free plan, which covers 50,000 retained users per app, or $25 a month on Pro. Better Auth costs $0. Auth0's Free plan covers 25,000 MAUs with a reduced feature set; once you need B2C Essentials features, 10,000 users cost $700 a month.
Is Better Auth really free?
The library is free and MIT-licensed, and there is no per-user fee. You still pay an email provider to send verification and password-reset messages, you pay for the database rows and queries your sessions create, and someone on your team builds and maintains the sign-in screens.
Why does Clerk's bill jump between 50,000 and 100,000 users?
Clerk Pro includes 50,000 monthly retained users for $25 a month, then charges $0.02 for each retained user from 50,001 to 100,000. At 75,000 retained users that adds $500, and at 100,000 it adds $1,000. Clerk counts a user only if they return at least a day after signing up, so sign-ups who never come back cost nothing.
When is Auth0 worth paying for over Clerk or Better Auth?
When a customer's security team requires SAML or LDAP federation, when you need Actions that run custom Node.js code inside the login pipeline, or when procurement has already approved Okta and will not review another identity vendor. For a consumer or early-stage SaaS app, Auth0's rate of about $0.07 per MAU is hard to justify against Clerk's free tier or Better Auth's $0.
Should I start on Clerk and move to Better Auth later?
It is a reasonable plan if you budget for the move. Clerk lets you export users, but switching still means replacing SDK calls and middleware, rebuilding the sign-in screens, re-testing every sign-in method, and handling password hashes and active sessions with care. The cheaper time to choose Better Auth is before launch, when there are no live sessions to migrate.