I don’t think anything is being artificially made unavailable to keep prices up.
I think making Boba Fett helmets is time consuming and when businesses like RS Props are primarily providing other products (like vacuum formed products which have a higher ROI for their time on task) and companies like MachineCraft (that primarily offers metal products, but did a run of G2 helmets) then you’ll have to wait until it is convenient for them to make more.
If you’re unwilling to wait, there are G3-G4+ helmets available or you could buy a previously owned G2.
Like others have mentioned, everything Boba Fett that’s worth doing takes a much longer time than most people are used too.