Prices on "Amazon" can change quite rapidly, esp on stuff Amazon doesn't sell. It seems on items Amazon doesn't sell, they rotate every day or so which 3rd party price gets quoted.
The 4 models listed on Amazon all say the "International Version", which I'd assume means the RM-984. If so, then they'll work with AT&T on HSPA+, but not on LTE.
For full AT&T or T-Mobile compatibility, look for the RM-983 (AT&T branded version), or the RM-985 (Canadian and Latin American version).