alt Hacker NewsGOV.UK pay has done £9.2B in payments in the last decade, with an average of £67
https://www.payments.service.gov.uk/performance/
A very crude calculation for £1B a year in payments (thats probably too low) would mean a payment to Ayden (contract is upto £25M over 3 years) of 0.8%
Most of the things I pay on the government website (except vehicle tax renewal), so basically tax, I've been pushed towards a one-off direct debit each time instead of a card payment.