So far, I hadn't seen much of these butyl based products in hardware shops as they are specifically made for automotive use. I know this would sound like hard selling, but RAAMmat BXT II(which I'm selling), which is butyl based, comes down to roughly RM12/square feet(if you get in a box of 24 pieces covering 37.5 square feet), one of the cheapest in the market at the moment.
..Ive done all four doors on my kelisa using the sound dampening product from Mohawk,overall yes the door feels much more solid even after knocking it and opening and closing..But in my honest opinion it doesnt really make much difference even with my fullset ICE installed,its not really a value for money kinda thing..Its more like an accessory that people think is useful but as a matter of fact its not really that great..Unless you do the whole car which will cost you quite an amount and the results might differ,just my point of view on this matter 
