“Can one pay say a maintenance place to build a kit aeroplane? Would it be cheaper than a factory built one?”
No and probably not. The probably not depends on instrument fit. If you were to put the latest synthetic vision system into say a TB20, it would cost a huge amount of cash. One of the big savings on the LAA side is you can fit uncertified but equivalent kit for around 3 – 4 k. Leave out the avionic fit and you are unlikely to save, but you could get a more personalised result.
My idea of a known quantity is to have built the thing, know it inside and out and know it was not built in a rush or down to a price. When I take my nearest and dearest up, I find that helps a lot.
Rod1