Adyen is an "interchange-plus" payment processor, which means they pass on the interchange fee charged to them by the payment processing networks, plus a fixed markup.

Stripe is a flat-rate payment processor: 2.9% + $0.30 on everything.

Interchange fees range from 0.05% to 3.2%, more or less. Most consumer cards are going to be significantly cheaper than 2.9% to process. Many people use "check cards" from their bank which are in that 0.05% category, for example. American Express and the top tier Visa and MasterCard rewards/business cards are the ones where interchange can exceed 2.9%.

There are many "interchange-plus" merchant account providers now. I get better rates than Adyen is advertising on their website right now.

They built an incredible amount of infrastructure to support it, better than anyone due to the fact they were all ex payment execs. Business cards are nuanced and they didn't focus on it, though they're about 1:1 with Stripe.