You are kind of asking for a lot of speculation here.
Most Kurz actions I have seen for sale - and that's not a lot - are in the $2-3K range.
Should be fairly easy to identify as original or not. Remember, they are all small ring actions except for maybe one or two known.

Is it a square bridge action or a standard round action?
Is it cut for a scope or unaltered?
If it is a rare configuration the value may be much more than the action alone and a shame to split up.
Are you considering it for the action alone?
All I can say is that Kurz Mausers are indeed rare and a good one is hard to come by these days.