There has to be a cutoff at some point. If the rule was "it charges you 15 seconds after you hit run" rather than "when you hit run", it'd not only be slightly more confusing to explain but also just barely help as usually (I've found) it takes a minute or two to figure out a bot is just broken. There are other similar ideas I've heard that would work though so I get your point.
At least Runemate only costs a couple cents to run a bot once, rather than other clients where you have to pay up front for a bot? + most premium bots here have lite/trial versions.
I don't have any solid numbers on Runemate's earnings, but I'm quite confident that the money Runemate makes from these situations (where someone hits run on a broken bot) are negligible compared to the rest. The majority of runemate's income is probably satisfied repeat customers, not random people spending 8 cents here and there randomly. I would still like to see a solution that satisfies these users having issues though.
This is a common condition that a lot of bot authors decide to have, that to send a refund they require bot logs and proof of payment of some sort, but it's really nothing to do with runemate's rules. It's just authors wanting a bit more info on issues before giving a refund. I'm pretty lenient with refunds but I also don't get requested them often.
I do agree the payment system isn't ideal or anything btw, I do have my qualms with it/things I'd change, but yeah, just giving my 2 cents.