Maybe its because PS3 users are loners? Why pay extra for something when the main benifits are social interaction.
Xbox 360 users have tons of friends, and thats why the extra social contact is worth the price. I mean people who talk up cross game chat/invites, voice in all games etc obviously have lots of friends right? I don't hear about PS3 users talking about having friends.
I met a guy at the local electronics store, and he was buying a PS3 because he was EMO and the black colouration of the PS3 fitted his moods better whilst the extra detail from Blu Ray helped him feel much more emotional impact from his EMO Rialto movies.
See? Proof, PS3 users are EMO and loners.
JK guys!
Actually its proof that anecdotes and misinformation are bad. 
Tease.
