1. The calculation for Logintap assumes that every user does daily logins into your system, so 22 logins each month. Meaning that if users return only once a week - your cost per 1000 MAU will drop 5 times to $0.0086 per 1000 MAU. Note - unlimited users stored, who can come back even less often
2. To be fair - (a) Auth0 service extends beyond authenication, and (b) Auth0 declares that a free plan exists with up to 7K users, however, the pricing calculator provides a cost of around $22.8/month for each 1000 MAU.