I don’t think it’s advancing technology that’s allowing this. It’s not physically constructing or programming a robot that’s so expensive, it’s iteration of designs to get to that point. A hobbyist can build a small working jet engine at home, but their hardly starting from scratch.

Further, building a modern full scale General Electric GE90 is extremely far beyond what a hobbyist can accomplish. If anything the true cutting edge is getting ever further out of reach. A few peasants could build a full scale trebuchet, good luck getting your friends together to build a F-22.