Here is Stripe (used by Kagi):
2.9% + 30¢ per successful card charge + 0.5% for manually entered cards + 1.5% for international cards + 1% if currency conversion is required
So if you pay $1, Kagi gets something like $0.65, meaning it just lost 35% on the payment processing fee. There is no way this can be profitable to serve the service.
