Once again you are comparing different models. As far as difference in Pro to Ironwood I can't tell different gauge steel or "better" materials being used but certainly can tell the difference with the features, down draft, double wall insulation, side self, etc. The difference in weight, which would be a great indicator that thicker gauge steel is used, between my Ironwood 650 and Pro 575, is only 25lbs. I can see that the side shelf , larger cooking area, double walled insulation, caster wheels, would make up for this 25lbs. Not thicker steel.
You must have talked with someone who is not familiar with manufacturing and vendor laws. Models are all the same across EVERY Traeger dealer. What models they carry (Pro, Ironwood, Timberline) may differ. The Pro 575/780 is the same at Home Depot as it is at Ace Hardware.
If better materials were used on the Ace model it would have far different shipping specs (would weight more or less) but most importantly would HAVE to be a different model number.
I don't own one but have looked at the Silverton at Costco. Outside of a lighter hood (which could allow for cheaper build) it is a fine grill and worthy of the Traeger name.