Blender dev here. A majority (like 2/3) of the development nowadays happens through the core development team: it's around 30-40 full-time/part-time paid developers. Most are located in the Netherlands. We make an average salary that's slightly higher than the average in that sector here in our country. All of the money comes exclusivly from the Dev Fund (fund.blender.org). It's all donations, no strings attached. We say "thank you" and (if they wish) put the logo on the website.