Paying developers to do work definitely helps.

The lead developer of GIMP currently receives about €1,200 per month in donations via PayPal, and the entire GIMP project receives even more via LiberaPay. Admittedly, this is not really ‘their paid job’.

But now I've had to listen to open source fans for over twenty years saying that open source software shows that you don't need a lot of money, just a lot of volunteers to do much better work together. I don't doubt that (for example) Blender is excellent software, donations or not (they didn't always exist). But why does this concept fail when it comes to image editing software?