I've been researching deadeners myself, I have a pricing spreadsheet of the ones I'm interested in.
I wouldn't call it pricey at all. Kno Knoise (80 mil) is on par with Damplifier, and cheaper than both Audio Technix 60 mil & 80 mil. Kno Knoise Kolossus (100 mil) is on par with Audio Technix 80mm and cheaper than Damplifier Pro.
I'm trying to find some information about anyone that's used it.