Image editor that's close-ish to Photoshop.

Really good RAW-converter/image library, especially if it's cross-platform. The open-source solutions aren't really bad, but a good one would be worth money.

IDEs and various dev tools potentially.

There's definitely a market. I don't know how many times I've heard people say they would switch to Linux but can't because of some critical app they need. The 3 I hear about most often are games, MS Office and Adobe software, usually Creative Suite and/or Acrobat Pro. I think there would be a market for engineering and design software too. AutoCAD, Matlab, etc.

There's WPS Office to replace most uses of MS Office.

I pay for https://www.insynchq.com because I became tired of all the tools that just couldn't sync with Google drive.

Thanks for the shoutout! :) We're always happy to help out the Linux community.

-Greg from Insync