10€ extra total, 8 extra for Tidal instead of Spotify and 2 for a paid email service.

But that’s not an entirely fair comparison, Tidal is a better service than Spotify, and there are plenty of free email providers to choose from.

I believe that it’s specified in the architectural reference framework that it has to re-validate every session, to ensure that the token hasn’t been revoked. I’d be happy to be corrected, though!