Worked for a plumbing supply house as vp of purchasing for 20 years. Been retired for a year+. Faucets from major brands can have plastic traps, stoppers and more. The complete part numbers are different. Other items have consumer grade specs. Stainless sinks are thinner 22g vs 18g where they have different versions for price. I don't think toilets and china are different. Flush valves and flappers might be, but again, full part numbers are not the same. The AO Smith water heaters are the same, but sold with a different warranty. We didn't do much in tools so I can't comment there.