Agreed, there are many cheaper alternatives out there. If I was on a tighter budget I would have considered them. Ebay has a plethora of knock offs which I'm sure are just as good. At the time I started building the truck, I wasn't married, didn't have a mortgage and had some extra cash. Well those days are long gone! If I did it again, I'd find another simlar product.
Garry
From my reading of the area of concern (drivethrough windows) I don't think dynomat or anything else will help. They are intended to quiet down the interior. The noise of concern here is mostly coming from under the car and creating the issue. Possibly rubber baffling to block off as much of the open areas below the engine as is reasonable without interfering with suspension travel is your cheapest approach.