but there is a threshold when the price compensates for risks taken. Porsche / F550 (4 times that price) are no more/less troublesome. I am lucky enough to have driven both and if I was heading to the south or france in a day it would be the Merc everytime.
I think they'll get to a similar level as the Porsche 996 and Jaguar XKR. Ropey ones are dipping as low as £8k, but a good one would still cost £12k - £15k. With the potential risks of buying these cars, condition and service history is everything.
Not a 500, but something like an early SL350 with the 3.7 litre M112 engine and coil spring suspension, would mitigate against most of the major issues, leaks aside.