If i compaire the prices of games and their quality than i think its ok if GT5 will cost beetween 100-200 dollar
a very good example

iam a big cod fan)cod 6 had cost 60 euros in germany but the game wasnt worth it (i will never buy a IW game)
the game has so much problems and it feels like it is only a small update to cod 4 ...if i compaire cod6 with gt5 than it have to cost beetween 100-200 because you cant find a other game on the world which is so focused on details
you know how PD make the cars (all cars are 1:1)they need 1-2 month for 1 car ,watch the GT5 SLS amg video and you will see (or watch the nascar video there you can see too that they are make pictures and videos of the cars...)
normal games need 1-2 years to be finish=50-70 euros
GT5 is 6 (iam not sure but i think 6 years)years in development =100-200 euros (the game is a little bit more worth but i think you cant sell a 250 euro game )