As far as I understand it though, the Team has an overhead cost. e.g. 2 x individual Pro subs = €18.44 x 2. The Team sub = €29.99 per user per month, min 2 users. Their subscription page just says the Team plan has "even higher limits."[1] What does that mean? How much higher for the extra cost each month?

Essentially you are right, I could stack subscriptions via a Team plan, but for a premium.

[1] https://mistral.ai/pricing/