the laugh is you can make Rolls Royce compressor wheels for around hundred quid each, yet they become £ 2000 " to cover R and D" that was paid for by the US military in the 1960's. A gas turbine is very simple to build and actually cheap to build. It is just the manufacturers saying, oh its aviation so we will take the piss. As for safety compared to the car industry aviation is mickey mouse , just ask my QA manager who used to do it for JLR before as he says going into the dark ages on safety by working in aviation
So i dont see why he can build one, why does ne need his own autoclave unit ? Cabri didn't have their own to start with yet they can build a certified 2 seater for euro 300, make it a bit bigger with a gas turbine, Robinson did it with a certified RR 300 ( a slightly modified 250 ) on their 66