First, there's a lot of developers scratching their own itch as you say. Second, there are probably more paid developers for desktop work than you think. They w

First, there's a lot of developers scratching their own itch as you say. Second, there are probably more paid developers for desktop work than you think. They work for Red Hat, Suse, Valve (not necessarily directly employed by them), AMD (excellent drivers these days), Blue Systems (a philantropy organization supporting mostly KDE), the Qt Company, etc. If you add up all the paid developers working mostly for the benefit of desktop Linux, and "partial" paid developers whose work somehow benefits desktop Linux, it's probably several hundred at least.