I kicked off at my previous co because we paid ~3% on Clearpay transactions, let alone 4% - 8% of turnover!
1% Elavon 1.6% + 20p Paypal 1.6% + some fixed fee Shopify payments (Stripe) 3% Clearpay
We paid one of these fees per transaction. Clearpay is similar to Klarna, so we were accepting some of the credit risk of our customers.
Paypal was annoying for foreign currency, as there were exchange fees, which weren't made clear and harder to convert back to GBP.
My issue with Clearpay was that it was hard to identify if it was meeting our objective, which was getting higher value orders.