If I had a mil and a half laying around there's a lot of really cool airplanes I'd consider buying.
A Navajo isn't even kinda close to one of them. It's a slow, inefficient, loud, dying old breed that's only going to get more costly to maintain.
This guy is no different than people who restore cars, boats, guns, houses, etc. You take a junk frame worth X and add Y amount of crap to it, you don't get X+Y+even more just because you think it's nice.
The Baron and Diamond while similar price wise won't hold the same amount of people in the same comfort. but when it comes down to it, there's nothing this thing will do that a twin Cessna can't do in pressurized comfort for far less money. Any cabin class piston with a 430W is just as capable.