Specs on Academy website say 14 gauge, with 11 gauge doors. From the "feel test", they're much thicker than the OK Joes at the box stores, but not a full 1/4" plate.
As far as justifying the more expensive one--only you can do that. I'm pretty happy with mine so far (only about 2 months old). I sealed the doors with stove gasket. I used the plate they provide for coals as a baffle plate, flipped the fire box grate and use it for my coals. Runs a pretty consistent temp left-right (about 3* variance). I'm happy, and appreciate the extra money in my pocket, but I'm just a hobbyist, and don't cook for big crowds.