(I work at Stripe)

We've encountered a lot of customers that are paying much more than they should be for a merchant account and gateway setup. Stripe's fees start at 2.9% + $0.30 per transaction, we don't have any hidden fees, and we offer volume discounts for businesses on track to do $1MM/year or more. Separately, PayPal has many add-on fees ($30 per month if you want to design and host your own checkout pages, 1% cross-border surcharge, 3.5% transaction fee when your customers pay with American Express, etc.) which often make it more expensive than Stripe.