Some people collect these but to be of interest to a collector it needs to be complete, original and in very good condition. Otherwise it's a "shooter" and I see these from $75-$250 in most cases. A nice, original Cavalry Model Krag (short barrel) will bring $1,000 or more. I have a sporterized Krag that I paid $85 for in 1992 and I bought a similar one for $75 about 6 years ago that I sold to a buddy who wanted one.
Like most guns monetary values can vary wildly depending on many variables.