There's 50 square foot rolls of Black Mat Premium sound deadener on eBay right now for $79.99 'buy it now' price. http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=5792589397&category=67760&ssPageName=WDVW&rd=1. Has anyone used this or heard anything about it?
I found they're web site, but it doesn't have much more information than the auction. http://www.perfectionsound.com/index.html. Of course they claim it's the best, and it's 70 mils thick...but I haven't heard of it before.
BTW - I've been looking and reading about roofing membranes (Peel-n-seal, stuff from Home Depot, etc.) and they definitely seem cost effective, but I would imagine these are all asphalt based instead of butyl based. Wouldn't it be better to use butyl based products for this application?