Probably a first rate machine in its own right but my first thought and concern is that being a "one off" that parts access could be almost nill in the case of a failure....price should reflect that possibility.
What parts? I've owned maybe 30 or 40 machine tools all second hand, some over 100 years old, many needing extensive work and I've never bought an OEM part. (hope I didn't just jinx myself lol). The stuff that wears out, bearings, belts, motors are commercial items, other bits and pieces you make and for wear you scrape.
imo its priced right, if as well made as it general appearance hints at. They don't sell by the pound, small stuff you can get down stairs that is in good shape should command a premium. Usually home mades are worthless because they are hack jobs....but that looks bloody impressive. Still, imo unless it performs some extremely unique function, its a misguided endeavour...if it is worth 4,000 the poor guy was working for less than 3 cents an hour lol.
Part of me me would like to go buy it, but with 7 mills/jig borers I haven't the space or need....but it looks a unique and nice machine. hmmmm.....where I can squeeze it in!?