Why not 30k or more for a car, which has such a low mileage and if it´s in a very good condition ?
Just saw a local private app for a Alfa Bertone 1300, completely rotten, for 18 tEUR. Ok, that´s really bullshit, but I know, this guy will sell it for around 12-15 tEUR. There are many other cars underrated, a friend brought a nice Fiat Sport Coupe 1966 or 67, 1st series from Italy, the Lampredi engine with a 5-speed, very fine, for not even 8 tEUR.
So, keep your prices up, it should be a target for a community.
And, I do not agree with higher spare prices etc.
Spares for my former 280SE 3.5 which will be sold between 20t-50tEUR, are cheaper than the Rover ones, it´s more depending on the number of cars and so number of companies offering spares. Due to the wide range of other RV8 models, motor parts will be affordable for a long time. Yes, for more specific P6 parts, prices will rise and parts from later series are not interchangeable (as in many Mercedes, Porsche, Opel, Ford etc are).
The Merc club where I am member too, has a huge (huge !!!) spares warehouse, they are traveling each year to US scrapyards and send back 2-3 40" containers. They also offer new spares, manufactured in small series, for very low prices on a non-profit base (Just to run the club). But it´s not comparable, the Mercedes scene is "huge" and these special guys spend all of their time, their holidays, it´s incredible.