The thing is in Germany you can never get a car this rust free, so it should be worth a lot of money there. They spend that much to replace just the sheet metal and then the car is still just a (hopefully) fully restored car, but not a factory clean original...
IMHO, TUV inspectors care about rust but don't care about how it was repaired...I have seen a lot of lousy rust repair work over here that passes inspection but is not even close to concours or decent repair work.
As a former global economist, all I can tell you is that every financial bubble has the same pattern, where folks extrapolate current price movements as a real trend, every bubble takes that trend PAST fair value due to over exuberance and then recent buyers for gain or emotional gain panic and push the market down past the fulcrum point when prices peak.
The other reason for these newer collectibles is that it is hard to find a decent mechanic for the oldtimers here, most are retired....many shops won't even touch our old cars, they don't know what a carb fueled car is.
BMW E9 cars in good, not concours condition over here are less expensive than in the US because there are more of them over here, it is a nice arbitrage but with prices going up 20% per year it is almost game over on that! it absolutely amazes me that M3, M5 and M6 cars here command such prices, mostly because Porsche prices are insane right now for just about any decent 911, that pushes buyers into other fast cars brands because the desire for speed outweighs the logic, another sign of a bubble for sure.
With global interest rates at about zero except for higher risk credits, folks around the world with some money want to spend it rather than save it, for longer term bond investors, and most German wealth is in bonds, they will probably lose less money on these cars than when the artificial bond market rally led by central bankers reverses and interest rates rise.
It's just too bad every highway in Germany is being repaired now because they spent the last 20 years in reunification. At least they will look good stuck in long backups on the autobahn, hope they make sure the 20 year old AC works!
Sorry about the rant, but it's time to take the old E9 for a ride in the Eiffel mountains near the "ring". Have a nice weekend!