So, I'm in probably the same predicament as most on this site.
When I got into RPGs, I was young, which meant I had time and energy, but no money. So I borrowed a 1e DMG from a friend, a Basic/Expert set from another friend, and ran from those until I could finally scrape together to buy my own. I relied on donations of dice from older gamers or sympathetic parents, but we ran games daily (sometimes multiple times per day). I probably wasn't the best RPG customer, because I didn't have a lot of money to throw at RPG companies, but boy, did I play the games into the ground.
When I got older, I had money and energy, but no time. I didn't get to play for years at a time after I had kids. I did use money to put together a deep bench of PDFs on all sorts of subjects, mostly to save me the time of trying to figure out/create/write the rules for such things myself. I also took it upon myself as a responsibility to pay things forward by purchasing RPG supplies for my kids and their friends (who wanted to play and had time and energy but no money) - mostly core rulebooks and dice.
I'm not yet at the point where I have money and time but no energy (hopefully in another couple of decades).
Presumably, the industry has to target people when they are in the "money and energy but no time" phase of life. When you have time, you are more likely to create your own stuff than to spend money on other peoples' stuff, and when you lack money, well, you can't support RPGs even if you want to!
So now when I'm making a purchase, I tend to ask myself, "do I want products like this to be around for me or for others?" It's less about "will I get pleasure out of this" and more "is this the sort of product that will allow others to find the same joy in the hobby that older products brought me?" There's also a bit of, "do I think others will support this company if I don't?" Most of all, though, there's the question of "when I reach the point where I have money and time, will I want to use this?"
So I didn't buy Daggerheart, for example. I'm confident CR has enough fans that me purchasing their product won't really make an appreciable difference in their margins.
I don't purchase new D&D stuff any more, either. I don't think my business makes much of a difference in WotC's bottom line AND I'm also not certain I want to support their business (still have a bad taste in my mouth from the OGL debacle).
I won't be purchasing Starfinder, but I have purchased plenty of Pathfinder-related stuff and still think I will do so in the future. I like the system, I don't KNOW the company, but I've met some of their folks in the distant past and I have no reason to dislike the company.
But I have put together my own distillation of the Pathfinder Rules for my homebrewing, and I think if push came to shove, I could write a game that like well enough to at least play at my home table. Or play games from the past, goodness knows I have enough of them (looks at every version of D&D since 1979 on the bookshelf behind me).
What I can't do without an unreasonable amount of effort is make beautiful-looking things like art and maps to enhance my game That sort of stuff is not in my wheelhouse. So most of my RPG budget these days is spent on beautiful battlemaps, tokens, etc. (usually in VTTs). Because I want these kinds of things to flourish and get better and be around long into the future.
You really want to take my money? Make animated battlemaps of the older WotC modules (especially the B- and X- series, I would love an animated Rahasia map) so I can use my older text adventures with new, pretty, graphical imaginings. I know WotC fan content policy means you must give those things away for free, but if you're giving them away for free and I think they're pretty, I'll support your Patreon for a while, even if I'm not thrilled with your other stuff and am not actively using it.
As to price limit, I'll usually drop up to $20 without really thinking about it if something looks interesting or funny. If it looks beautiful or scratches an itch, I might drop $50 on a whim. Above that, I have to have a specific reason why I am supporting you - it could be just because it's a beautiful looking book or a great rules implementation or something, but I can't justify more than that as whim-spending.