> $0.02 per MAU > Free under 5K MAU Is that 2 cents per user authentication? I'm working on an application for a car parking company and I was planning on doing a passwordless auth approach. Problem is they will likely have about 10,000 different bookings a month and very unlikely that they will log in other than to check their booking. Trying to justify the cost which would be fine if it was for any other kind of system, problem is this is for users that will likely log in once a year if ever.

It is not per user authentication. MAU stands for monthly active user. So they will be considered a MAU in the month that they create the account (signup). If they do not login or check the account in the subsequent months, they will not be considered a MAU and will not be billed. From a billing perspective, users will be considered as active only in the months that they use your solution