So the cars wont sell and i cant change the price.
Hey,
with 1.10 there is a new game mechanics related to car upgrades and pricing.
Maybe this post will help you tp change your premium/discount when it has passed 100%:
http://positech.co.uk/forums/phpBB3/viewtopic.php?f=57&t=18257&p=84395#p84395
Depending on you production output a premium/discount of 40 to 70 % can be usefull.
Kind regards