This is kind of the tradeoff you need to make when launching a product though. You cleave off some of the product's margin & send it to a third party so that you can get the thing launched. If it's unsuccessful, that's fine, you'll pay no money to the vendor. If it's successful..? Great! Now you can afford to pay someone to build a checkout that doesn't cost me thousands a month in fees.
Stripe takes 1.5-2.5%, so if you're sending them 1,000s a month, your revenues from that checkout are approaching the $millions p/a. Certainly enough to hire an expert in the domain.
Stripe's fees are well above interchange fees (especially in Europe). On top of that Stripe's pricing for other features (e.g. invoicing and subscriptions) is also a percentage, so you end up paying a ton for those features.
because stripe on purpose hide fees, constantly asks you to try out new features and then secretly charges you more then market price when you say yes. See radar, managed payment, stripe billing management etc.
Stripe takes 1.5-2.5%, so if you're sending them 1,000s a month, your revenues from that checkout are approaching the $millions p/a. Certainly enough to hire an expert in the domain.