A uzi is on my list of guns to build, Cetme type C 308. (there are lots out there the receiver flats sellout fast), mp5(one day that one is pricy) got a laundry list of ones to build. Parts aren't that expensive it's the jigs and kits needed to actually build it that are the main cost. Usually some require a press. Straightening jig, welding jig, etc. But once you got it all its pretty cheap after the fact. A Ppsh is on my list but making it 9mm..
Just bought a Spanish Cetme type C receiver flat. Kinda hard to get these flats sell fast. Like the msg91(Ptr91) this will possibly be my most expensive build for just the tools alone. 300 for the press jig and such. 200 for a press...that not even the parts kit included. I'm just gonna build all the parts kits and 80%s I wanted and just slowly build each one over time. Even doing all that will take a long time. I can't go nuts here wish I had a few thousand dollars to burn on my goals. Lol
I'll warn ya now. A friend of mind did that, (the bits that need drilled out and are not serialized, etc) and he drilled it. His one major thing of advice. "Oh the fucking aluminum dust/shavings. They get EVERYWHERE" He drilled it out like a month ago and he is STILL finding shavings/dust from the process around the house. lol