The domain name goes pretty nicely with .mobi (communications network for mountain climbers on-go?), and was grabbed only 2 months after .mobi became publicly available for registration. I'd give it about $95-$120 it about reseller value.
Would some end-user out there pay $500+? You never know until you try pitching. I'd start with the folks at MountainGear.com since Mountaineering.com redirects there and that company's site gets over 500K monthly hits.