You are right Schro, however I do not think it is the right mechanism. Discounts run in the order of 30-40% of list prices but inflating the prices because a model is popular defeats the purpose in my opinion. The game aims to mimic reality and it is offered as a management tool, so what I am proposing is a realistic mechanism.
List prices should be just that, and possibly linked with real life prices and inflation. Discounts then should be heftier according number ordered and "likeability" e.g. an A380 lists at 400M at the moment, an order of 10 will yield a 10% discount and if the model is not selling then a further discount according to the airframe slot date is added like 1% per week away starting from, say, 6 months (24%). So if order 10 A380s and one of the frames will be a white tail within 3 months I will get a discount of 10% +12%=22% off list: 88M discount for THAT frame but not for the others.
In that way one can risk ordering at empty slots to get a discounts instead of bulk ordering. This would help small airlines buy the heavy metal (carbon)!
Having said this, I would not have a clue how difficult this is to programme!