It's true for things other than developer tools. I built a free utility that became popular and people started asking for more features. I spent several months working full-time on building out improvement and put 10% of the new features behind a paywall. I took nothing away and made 90% of the new features free too. The stuff I put behind a paywall is stuff I thought would only apply to professional business users. Just the fact that I had paid features made people upset. I got a ton of angry emails asking why the tool was no longer free. I also used to make some money via donations through BuyMeACoffee and those nearly completely stopped.