Are you saying you can't support the developer for 1 month with as much money as you want/can and then drop it? Isn't this equivalent on patreon as what you're trying to do on Steam?I do wish they'd release this on Steam. Happy to part with a one off payment for this game. I don't like the Patreon subscription model though. I get why devs do it and I do appreciate that it's a way of securing ongoing support. But for those who play a lot of different games it's unsustainable to support multiple devs. It might only be a little here and there, but it adds up. Which is why I like the Steam option. I've purchased a couple of good games that way through devs with a good track record. They'd also possibly reach a wider audience.
Needless to say with that caveat I'd never buy a game from a dev who's name starts with "I", and ends with "cstor" for example.
I mean, I see your point and it's perfectly reasonable but I think this problem is easy to solve.