I think you're a bit on the high side, if you want to sell these machines sooner rather than later. A new Chinese 6040, which is about the same size as your larger machine, goes for less than half that on Amazon: https://www.amazon.com/800w-6040-car...words=6040+cnc
It has profile rails, which are better than your round ones, and a real spindle rather than your hand router. The design seems more rigid than yours as well. It may be that your machines have some better features than it does, but they aren't obvious, while the deficiencies are. You should also take into account that people generally prefer new machines to used ones, and commercially built ones to home-made. When selling home-built machines, you should consider yourself fortunate if you get back all the money you spent on the parts used in building them.