I don't have a hard math here. But here's some example: JRebel. It allows for instant class reloading in JVM. It increases one's productivity tremendously. And it's expensive as hell. They used to have free version, they don't have it anymore. I can only judge that they're struggling and forced to squeeze all they can, because developers will prefer free restricted version over paid full-featured version. I know, I do, I don't value my own time and I'll never pay more than $100/year for a tool (and hopefully much less), I already trying hard to justify Idea subscription, because it seems that Idea CE contains almost everything I need.

If developers would love to spend thousands of bucks here and there, paid developer tools industry would flourish. But I think that it's even degraded compared to the past. I remember paid Delphi IDE and I remember paid components and that was a thing back then. I can't remember any popular paid React component right now, despite the fact that much more people are using React compared to Delphi.