Why don't they sell these car at discount?
Because why would you buy this years model if you can get the previous model new for a decent discount?
Another reasons is laws are always changing, particularly in Europe and particularly in regards to emissions, it stands to reason that often the previous model doesn't meet the requirements to be registered.
The solution is just not to produce cars they can't sell in the first place rather than producing loads and not being able to sell them all.
but for general terrorist transactions the market is nowhere near big enough. 
