More my personal PC, I'm also runing GP4 on a laptop which is a Dell latitude D600.
With it I get 25 image/sec for a mean PO between 40 & 70.
all 2005, 2006 cars with medium size texture are OK.
But no chance to use HR track.
regarding the cost, I don't know. It's my professional laptop and I did'nt buy it.
Hope this help you.
GeZeRe