I have a full set of calhoun's collectors society stamps - 1000 stamps in nice binders - how much is this worth?
Simply check eBay for a price comparison - however you should view closed auctions and not running auctions or shop entries as you want to know what the items really sold for and not what their former owners thought them to be worth: like so many items, stamps and replicas have massively dropped in 'value' and many folks still believe in ten year old book values or such simply because they can't believe that the market has long collapsed.
My essay on 'value' :
A Question Of Value
My essay on Golden Replicas :
The Gold(en) Replica Lie