Talk about thousands of units being built and few remaining, how about a Messerschmitt BF 109 with the original DB 605 still in. If I am not mistaken, the 109 was the single most numerous plane of WW2. Go find one today. Then of those, how many with the original supercharged Benz plant that still works. Along with the single Dora Focke Wulf, they are literally impossible to determine prices for. A few years ago, Black 6, the only airworthy one at the time, crashed when landing on grass whose underlying dirt was too soft. It is still being rebuilt. But I just found this file the other day. It seems that there are two airworthy DB 605 Gustavs out right now. The only two in the world. Turn up the volume and enjoy this vid. There is nothing like that unmistakable supercharged 109 sound.
http://www.flyingmachines.tv/page1/files/109.wmv
As to Black six:
http://www.warbirdsresourcegroup.org/LRG/bf109g2.html