It has been mentioned quite a few times (look up “sell items” on the discourse), so the devs definitely know people want it as an option, and maybe they will eventually find the time to implement it. That is if they think it’s a good idea I do btw.
I think this ability will be a Godsend to many people who are struggling with money. I bought 25000 gems to buy Illia and Morning’s Edge to fight my way through Summit’s Gate - I don’t know what I would have done without it. On the note of gems, when you reset your progress, does all of the 43k gems you got from the lifetime subscription come back to you? Or do you stay with the gems you finish with?