The screen size is a pretty big difference -- the 17.3" is just under 23% bigger (in terms of surface area) than the 15.6. Of course, that's not $1500 worth of difference.

I'd be interested to know where you found that, though. Newegg has exactly five laptops with 15.3"+ 1920x1080 screens with CPUs clocked for at least 2.5GHz. All are $1560+, which is about $200 more than 900 Euro. Two are out-of-stock Toughbooks, two are recertified MBPs, and one is an absolute beast of an Asus that still has substantially lower specs than this thing. You may have found me my next laptop, assuming it will ship to someone I know.