As a former 'chef d'affaires' of a charity ride my take on this is ''**** the **** off'. It's not even about the money, it's about the spirit of the thing. It's about the effort, often unpaid that goes in to running these rides. It's about the additional complexity of running a ride swollen by people who should be doing it on their own. It's about the fact that the charity will barely break even on the ride entry fee, if that.
The money takes a long time to come in, but, when it does, and there are a percentage of names with a zero them (or some pony little single contribution) and a quick shuffle with Excell takes them to the top or the bottom of the list. You ignore the high-rollers and compare them with people who have collected small amounts adding up to, perhaps, a hundred quid. And then you look at the list again, remember all the encouragement these people had sucked up and wish a thousand punctures on them.
Give them a hundred quid or do it on your own.