I don't know about the density of the casting, but the quality of the clay is one of the reasons Toto locates their manufacturing when the do. There very well could be some of the finishing techniques that go into the better quality toilets as well. I have two Toto toilets, neither have the Sanigloss options, but I have no staining problems in either one. The cheap toilets found in Big Box stores are referred to as "builder grade" because the are cheap and building contractors construction spec houses buy them. They could care less how well the perform or if they stain, because after the house sells, it's the buyers problems. Many plumbers make a good living replacing these cheap toilets with quality just a few months after the house is purchased. It's human nature to want quality for cheap, but it rarely happens. Unfortunately, paying ahigh price for famous old name brands alone does not guarantee quality either.