Actually, your body is the only source of heat, regardless of what you think is going on. Bag efficiency is based solely on creating dead air between you and the outside environment. We have had this argument over and over, but the physics of it haven't changed since the first animal hide was used as a blanket thousands of years ago.

I took my new (to me) down bag to A16 to get it cleaned and while I was talking to Peter, the salesperson who helped me, he wrapped the bag over his shoulders. After a couple of minutes he said, hey, I can feel how warm this thing is. That's what it is all about.

Gershon, I would start looking for a used bag. I used Craigslist Reader, a free search program made by CraigsPal. This program will search any and all Craigslist sites on the planet. I found my bag using it. I've seen a number of WM bags. The prices people ask on Craigslist are usually better than on eBay, but be patient, some amazing deals show up. The only catch is that Craigslist sellers aren't always willing to ship, which the usual on eBay, but if your email looks legit and you are willing to pay in advance (I use PayPal), some will. I've bought several things that way and sold a few as well.

A bag seems a really personal item, but you'd be surprised the number of high end bags for sale that people say they bought then rarely used. The Marmot I just bought looks virtually brand new. The seller had both sacks for it (cotton storage bag and stuff sack) and even still had the original hang tag for it.