Put your user count and growth rate into the calculator to price Clerk, Auth0, AWS Cognito, Firebase, Supabase Auth and WorkOS side by side. These are the questions to settle before you trust the answer.
Most hosted providers are free below a user count and then charge per monthly active user. The jump is in the pricing model, not the user count itself: a provider that is free to 50,000 users can cost nothing where another charges hundreds of dollars a month.
Vendors define it differently: a user who signs in, a user who refreshes a token, or any user with an active session in the month. Read each definition before comparing, because the same app can have a different MAU count under each.
Enterprise SSO and SAML connections, SMS multi-factor codes, B2B organization features, custom domains and support plans. A cheap per-user rate can still produce an expensive invoice once one enterprise customer asks for SAML.
Not on price alone. Compare the 12-month spend under your growth rate, check how hard it is to migrate users out later, and confirm the free plan includes the features you need in production.