How much could I sell my 2 yr old rig for?

[Sqirk]

My friend wants to buy it off me but I don't want to overcharge. Thanks.
specs: http://pcpartpicker.com/user/datskid/saved/kHk7YJ

 

[tiny voices]

$500 max. Probably less because it is a friend.

i5 3470 used - $145
motherboard used - $50
RAM used - $45
7970 used - $130-$140
SSD - $80

These are prices for individual parts. Together in a ready-built used PC, everything is worth less.