Let's be clear. The free ones aren't given away necessarily because people feel good about it, it's a form of promotion.
When I really ramp up with Wedge plugin writing, I'll be giving a lot of them away for free, but I'll also have some paid plugins that will be much larger and much more complex (and thus require more of my time to support) - the free ones will be promotion, and the paid ones do things like pay for the server and mean that I can spend more time working on the platform as opposed to unrelated consulting work. I rather suspect something similar is applicable here.
Free is good, but only if that's what the market will support. Stuff shouldn't just be free 'because'. Free stuff gets written because people want to write it, paid stuff gets written because people are prepared to pay for it. That's how free market economics actually work.
And I think you're missing the point about people being rich or not. You do know that not everyone insists on financial contribution for everything? For example, I've donated subscriptions to people in the past for other things they've done. I've also bought subscriptions for things not because I needed them or anything but because I wanted to contribute something back when I didn't have the time or resources to do anything else.
There's also an element of respect there, too. I find that in most of these ecosystems, those who take and take and take don't have a lot of respect for those who keep giving, even leading to some cases of people taking other peoples' work and changing it very slightly, and republishing it as theirs. It's hard to keep releasing stuff like that when there's that low level of respect in there.