What would be a good percentage or sq ft price for materials only for an average 2500 sq ft home in Montana. What about a 10' deep sq foundation that is daylight in the front? I sure would have thought Google would have come up with several relevent pages but it didn't

Way too many variables.

Here are a couple of sites that might help.

http://www.building-cost.net/

http://www.home-cost.com/template.php?sectionID=10&pageID=44