Take care, Saliih. Read your EULA. What you bought from Nevercenter is a license to use the software, not the actual software itself. You own nothing. In fact, as outlined in the EULA…
I suspect that Pixelmash’s license is quite similar. You may no longer use these apps, but you still can’t resell them. Your rights are non-transferable. This sort of user locked thing is typical of EULAs and has been common place for at least the past 15 years, if not longer.
In part, companies do this (prevent resale) so that they can continue to rack up new licenses instead of recycling old ones. Additionally, while you may be honest, others might not. They might sell the serial numbers multiple times over, which isn’t legal.
So, like it or not, you’re stuck with your purchases. Sorry.