alt Hacker NewsI think I have donated more for Inkscape, Gimp, Firefox, and Libre Office than I ever spent on proprietary software. I also tend to buy paid versions of open-source apps in app stores, where available. It's great when a piece of open-source software has an easy donation link / button.
That said, I tend to trust all closed-source software significantly less, even if it's given away for free. Especially is it's given away for free.
Without knowing how much you've paid for proprietary software, that could be a lot, or a little. If you're coming from a position where there is alternative FOSS software available to use, that's your bubble/sphere of experience. In other realms, say software for doing aerospace CAD, there is no FOSS available because it's just such a niche piece of software.