tblack wrote a review of Marmot Helium MemBrain Sleeping Bag: 15 Degree Down on September 11, 2011
Clear Michigan January sky, stars bright as headlights, 15 mph wind, -10 F.
Slept on a tarp, z-pad, a thermarest and with a poly bag liner. Warm and cozy!
Of course I had all my clothes on, two hats and a light pair of wool liner gloves. But I still pushed this bag 25 degrees!
If I slept in my MH EV-3, I probably would still get a great night's sleep at -20 degrees.
Don't think about the cold money, think about a warm sleep. Sweet dreams!