There is an almost inexhaustible supply of potentially airworthy Spitfires, given that airworthiness authorities like the CAA will let you "rebuild" one from little more than the manufacturer's data plate.
One of my hobbies is WWI aircraft. With sufficient technical information, you can build the airframe, but obtaining and supporting an original engine is very difficult. When the supplies of engines and spares are used up-as they will be-the WWII and cold war aircraft will be grounded. Then it will truly be a rich man's game.