I too have accumulated several (many) sgian dubh knives, and knives that stand in for a sgian dubh.

The least money for the ones that I have kept, has been $22.50 (ebay) and the most has been $130.00. I think the mean price for a usable blade in my mind would be around $75.00.

However, I also have a few that I would not part with, so I consider them priceless. A few were acquired through trades, A couple were made for me as presents, and a few I made myself.