hmm i think even if biased GT4 way of selling olders cars is ftw !
I mean you can buy old cars with great mileage. But if you try to collect cars with low mileage you are seriously goin to spend weeks to buy some old car with 10km/mile mileage.
The thing i hate is winning cars as prizes EVERY TIME !!!
This destroys game economics. Buying TOYOTA GT-ONE isn't any pain since you have special missions where you get some WRC cars sold for 250k each..
Best possible option for me will be just unlocking possibility of buying that car.
Next neat idea would be like Ferrari thing. You can't buy from them Enzo till you have more than 2-5 ferraris (like in real life).
Also i don't like idea of buying from company dealers cars like Clio V6 that was only 1000 models produced...
same with charger, bugatti lm etc. Legendary cars thing shold be like showroom or museum without possibility of buying cars (like mercedes museum)
This rare gems should be bought by you in used cars dealers part. And then mileage should be more like death to a car. 10 km mileages should be goin for 10x or original prices not by 0,60 ...
Also when you are selling car it shouldn't worth 10k when you invested in it 200k.
Also cars that winned some racing events like le mans or 24 h should be gaining boost in car price. (thre is boost but it's toooooo small)
Also owning lots of cars from the same producer = discount...
that's my 50c ..
edit.
and last one thing neat idea would be getting a sponsor and racing team. They will provide you a car for a race. AND ONLY FOR A RACE. So it isn't your