The Marmot Helium is even more expensive than the WM Alpenlite, unless you can find a sale. The Marmot Hydrogen, at 30*, is definitely not going to work for those frosty nights in spring and fall, unless you're a really warm sleeper and don't mind wearing all your wraps inside the bag. The Montbell Super Stretch Down Hugger #1 is only $20 less than the WM Alpenlite. The only way to get a high quality down bag cheaper is to grow your own geese.

I agree, you get what you pay for. This is a lifetime investment, if you take good care of it.
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May your trails be crooked, winding, lonesome, dangerous, leading to the most amazing view--E. Abbey