“What would a high quality brand be? And how much do they cost?”
About 4 years ago, I bought about 6 space blankets from Adventure Medical. Good thing because I can’t find them anymore. They were in the $10-$12 range. It seems they quit making it. Their bivy sack is made of the same material http://www.backpackinglight.com/cgi-bin/backpackinglight/00055.html
These space blankets weigh about 5 ounces. One side is a white cloth type material and the other is orange. I use it as a ground cloth and place it with the white side up under my 2-man tent. Forest duff doesn’t stick to it like a polypro sheet does. This radiates warmth back up into the tent. They claim it’s a “Four-ply, waterproof, windproof Thermo-Lite® fabric”
So my blanket stash is holding out well. But in a year or 2 I’ll be in the market for a space blanket again. If someone finds a non-metalized-polyester light-weight space blanket, I would like to know!