But that's very vague. Sure, you can't have a $400k penalty on a $100 delivery, but online payment handling deals with incredible amounts of money, so a $400k penalty between multi-billion dollar companies doesn't seem out of all proportion.
The problem in this case would be that Stripe passes on the liability for the penalties to its customers if those customers are breaking the contracts. Obviously a problem for the customer, but also not unreasonable from Stripe's perspective. If you're setting up a marketplace and want to act as a payment-provider for third parties, you're creating a very different liability environment than if you're setting up an account to sell your own products. If you start with a seller-account and then transition your product into a marketplace, someone will have to eat that additional risk, and I can't see a good argument for why Stripe would be the one.