Some guy’s coming out with a easy ammo type swapping 3D printed blaster. Apparently he’s looking for applicants/people interested in the open Beta for it:
https://foamknight.com/He says once the testing and refining is done the files will be freely available and he’ll sell part kits and fully assembled blasters.
Only specs material cost-wise I’ve seen so far is that it took about 1 kg of PLA filament to print.