This has been a little trick for cheap asses in the car audio industry for years. For starters, that crap is asphalt based which is essentially the same stuff that comprised the original dynamat and some crappy knock-off deadeners. Any decent company and product now uses a butyl based mass. Asphalt was dropped because is stunk and became gooey in the heat. On top of butyl overcoming both of those shortcomings, it is also more effective as a viscoelastic material. Plus, the thickness of the foil on those roofing products is typically very thin; the thickness of the foil has a a lot to do with the effectiveness of the product. Do a google search on roofing materials as a deadener and soon I'm sure you'll realize how stupid it is. Right now Second Skin Audio is offering a blowout on B-stock Damplifier Pro bulk packs. Not only is Damplifier Pro the best product on the market, but it's cheap as hell, you're getting 36 sq ft for $115 plus shipping. If you're going to cheap out, don't even bother.
Not a good example to back up your POV.