The market determines what a used part will sell for. The Bembo calipers will fetch a fair price. That fair price is what someone will want to buy them for. You can ask a high price or a fair price and sell them quickly. From the 60's, junk yard rule was to get 50% of new part price first! then negotiate if it does not sell. Supply and demand still rules.
I checked on ebay to see prices. I did note that a set of 4 on ebay for over a $1000 did not sell, but I noticed pair that sold for $250. All you to do is look at the Completed Listing and you can determine what you can sell them for.