They (The display manufacturers) will be under huge pressure to fulfil orders, so chucking out a load of ipads because of slight variations in display temperature and backlight bleeding (Which is evident on practically every display in existence) would be costly, reduce the amount of ipads, and lower the amount for everyone, which reduces profits significantly.
When you are mass manufacturing the latest tech such as retina display, there are bound to be issues with quality - the problem is they probably can't afford to chuck away as many iPads with bad screens as Apple would probably like to if they didn't have profits to make and shareholders to please. Not to mention the millions of people wanting one.
The new retina display costs $60. Probably only 1/4 of them are absolutely perfect. So if only 1 in 4 displays is useable, you have to chuck the other 3 away. But you have already paid for those 3 displays, so you'd have to add on 3 x $60 worth of display to every iPad atleast.
Would certain people that work in photography or the media industry, or just wealthy people, be interested in paying a $200 premium, for a special version of the new iPad with much more stringent tolerances on display quality ? probably.