definatly be as coutious as possible in all cases good or bad. Then reality comes into play - US seems to hold 100% of face value for most lots on
ebay of $50-$100 worth, after that you need to start deducting in percentages of 5-10% If $500 face value go 90% if $1000 go %80-85% more than that 75% is fair on a bulk lot. Catalog is pointless for newer so don't consider the blocks, booklets and full sheets as a premium since most can still easily be obtained. I agree you don't want to cheat the guy but as 1775mac stated if you follow in house auctions the higher the volume the lower the percentage. Explain unfortunatly its a supply and demand issue and the supply far out weighs the demand in this case.