Standard hardware is 18 gauge, hinges with Steel ball bearing rollers. For Builder Grade type doors the hinges are changed to 22 gauge and the Rollers are plastic. The cost saves the purchaser (Builder) approximately 35 - 45 Dollars and the homeowner receives a less than satisfactory door that reduces the expected life of the door. Remember that the moving hardware is what wears out!
Time and time again homeowners think they save money by purchasing from the Hardware store they then they call a professional to install the material, it cost the homeowner more money. Home Depot says,"Do more/Save more." which means the purchaser is only going to save by doing the install themselves! A person saves nothing on material purchase because the pay full retail.