To address the OP and his question.

Western Mountaineering uses 30 oz of down in their 0F bags. That is just the down, no shell. Nanatuk uses 18 oz of down in their small 5F quilt. Because it is a quilt, it has less area to fill with down, and it still uses more than a pound of down and is not rated to 0F. So, unless you have an insulation that is lighter than down with the same thermal conductivity, then it is impossible to make a 0F bag for less than a pound. Well, unless, like others have pointed out, you are the size of my 5 year old.

You might be able to make one with aerogel, but then it would be stiff, like a board. You wouldn't be able to stuff it in a bag, or even drape it over you. It would be a solid block with a chamber in the middle to lay in.