Nice calculator; but it misses the currency conversion costs. You can't get $9.46 as a UK merchant - you get paid in £GBP and they add another 2% from mid-market rate - so $9.27 would be more accurate.
Stripe.com says Charges made in a currency for which you haven't connected a bank account will be converted to your default currency. A 2% fee applies for currency conversion, and all fees are calculated in the currency we transfer to you.
So you can avoid it by having an USD / EUR account. Or you have to pay this 2% fee. I will add a note to the page.