There are a lot of options for 'warmer' bags that don't come with the WM price tag.
If you compare a WM TerraLite to a REI Igneo for example, they're both 25 degree down bags, the Igneo is an ounce lighter at regular size, and the Igneo costs $269 to the WM's $485. Plus you'll never get a discount on a WM bag where you can almost always scratch up a discount on every other brand. Heck you could knock that Igneo down to $215 if you're an REI member right now. At that sort of price delta WM's warranty has no value at all (you could buy another Igneo and still come out ahead).
Just my 2 cents. I'm a total gear whore, but outside of sub-zero gear I don't see how they can compete with their prices.