Ok, I don't understand a few claims of some people in this thread;
-Bioshock is 44.95$ in a couple of my local gamestores whereas 'other' PS3-games are 60-65$... So the game frankly isn't full priced where I live!
-I think Bioshock is worth the 60$, who cares that it's 1 year old! It's about how the game compares to 'the rest'... And compared to that it's GREAT!... Totally kick-ass and better then most other shooters that are out there, in my opinion WAY better then that generic Resistance everyone is raving about!... I though Resistance wasn't that good! Just 'another' good shooter, nothing more, nothing less! Maybe R2 is better, I dunno, haven't played the game... But going on my playtime with R1 it's not nearly as good as Bioshock!
-Bioshock was listed as being released the 24th of October in a lot of my gamestores. Only 2 got the game on the 15th (actual retaildate 17th) and sold it right when they got it!
The date closes the 18th, so that's 2 official retail sale-days. Then 31k ain't good but not 'a bust' as the OP calls it!
Furthermore, I think the biggest debute will be in the US for the game, and the game will be sold by word of mouth and the releasedate fuck-up in the EU caused a cracked debute! I think 2nd week EU will be ~50k and US debute around 60 and 2nd week same... But we'll see!
I just wanted to say this; Although the game might sell 'not up to expectations'... It's still awesome! 
!!! Buy the game if you haven't already played it... It's up there with The Orange Box, Mass Effect, Metal Gear Solid 4 and Gears etc... The awesome shooters and action games of this generation!
THE NETHERLANDS
