The most expensive car list definitely needs a sales volume number to go with it.
If the MR-S has the highest average price and the volume of sales is 2 (i.e. a number that's very low compared to the average sales volume for other cars) then it's being used for currency exchange.
I believe most people use the cheapest car in their region for that purpose, I've used the Porsche 914 myself in the Europe region.
Of course, if the sales volume is high that theory goes down the drain.
The mini gets handed around for paint, it has a very flat roof which allows lots of artists to paint decals on the roof. It's the "canvas" car of choise for most logo/decal paints.
GT: Voodoo T10
The above post is my own opinion, not Turn 10's or anyone else's.