Ice & Snow rallies without studs are a great equalizer...car set up (soft!) and driver skill outshine horsepower...even trick diffs are no use when there's no grip at all. The podium for a snow rally commonly has different faces (Canadians!) than our gravel events...that being said, it's not much to look at from outside the car!

http://www.rally-america.com/thumb.php?pic=1988&max=600

Some of the current U.S. competitors from overseas have told me the same thing...~$500 USD per proper studded tire. An additional $2,000-$8,000 USD for a snow / ice rally seperates the "haves" from "have nots" of (already thin) American rally even farther. It might be workable with a less expensive limited or "spec" studded tire.

"Studless" tires currently used on snow and ice cost $80-$150 USD per tire.