AT&T PREPAID iPhone 6 32GB [walmart.com]
$245.59 + free 2 day shipping
$299.99 @ Best Buy [bestbuy.com]
$344.99 (includes $45 service credit) from AT&T [att.com]
Please be advised that if your intention is to buy and unlock the phone. There are reports that it's difficult to get AT&T to do an immediate unlock after purchase. You may have to either follow the terms by AT&T or use a unlock service to unlock it.
I bought this yesterday afternoon and received it today. I guess having the shipping center less than 100 miles from me helps. The funny thing is that it was selling for $266 then.