I bet you didn't seriously expect to get an actual proper answer to this!
When South Lakeland District Council closed the toilets in Grange we (Grange-over-Sands Town Council - I was on it at the time) took them over to keep them open. They were in a shocking state, the Gents in the duckpond were reminiscent of the old Goldstone North Stand toilets (yes - really). The Town Council took out a public loans board loan to basically rebuild them (and restore the old ones on the prom and in town). To fund the loan, the ongoing maintenance, and the cleaning, we started charging 20p cash. I voted against the charge, but in hindsight it was the deal-breaker. Not only did it help pay to keep them, but the way people treated the toilets changed overnight - that is, have a clean loo and people keep it clean.
Last year the council looked at going contactless because a) the cash was being carried along the prom with attendant risks, b) it takes people longer to find and put coins in leading to queues on busy days, and c) the cleaners had to spend time emptying the coin machines. Also - there were quite a few vandalism incidents related to the cash and the insurance was going up.
At the time, it was narrowly decided to keep cash (a lot of folk in or who visit Grange are old). Come the pandemic, and the switch to contactless became much more desirable.
It cost £650 per unit to convert, and the payment service for each costs £10 a month, with the provider taking 2.95% of each payment. The council also put the price up from 20 to 30p as the loos had been operating at a loss for some years.
So, in direct answer to your question: The contactless machine provider gets 0.885p per use, plus £10 a month - so less than 1p out of your 30p. The Town Council would get about 29p of your spend, which all goes towards maintenance and cleaning (there's no profit in loos!).
There you go!
Hope you enjoyed your visit.
Brilliant! I haven't seen a straight answer as straight as this for donkey's yes! Well done!