Aerogel winter window quilt?
Aerogel is brittle, easily damaged and extremely expensive. Thirty dollars per cubic inch sounds more likely than per cubic foot. There's a web site for aerogel and related products. The linked product is a silica disk, about an inch around and less than 3/8&quot; thick. US$35 fits in with the expected price.
The same site also offers composite blankets. It's a combination of aerogel and other insulating materials. Two feet by four feet by 5 mm for US$180 still falls into the expensive category, but that's my opinion.
There's no R factor in the main ad copy, but the spec sheet is available for download and may include that information.
Aerogel is silica and in powder form can be a problem if inhaled. Any product of that nature is a health concern. Don't shred it or otherwise damage it and the risk is low.