Looking at some of these "buy back" sites (like Gazelle, eleGreen, etc), I notice that if you select T-Mobile as the carrier then they are offering a good $60-$80 less than if you select AT&T or Unlocked as the carrier. Does anyone have any idea as to why it is worth significantly less? If anything, I would think the T-Mobile iPhone 5 (with the extra support for AWS/1700mhz band) would be MORE desirable since you can unlock these days without too much hassle and you can take the iPhone to AT&T's network without any problems. Anyway, does anyone have any ideas or input? Thanks!