[h2oya311]

my initial thought is that most "high end" items north of $1,200 sell for more at an AH vs. eBay (although 30% seems a bit high). Additionally, there were a few amazing 1937 OPCs in that Mile High auction, so my guess is that this helped drive up the price of the Greenberg a bit (seeing a few nicer examples in one place might help drive up bidding). Mile High does have a pretty wide audience of collectors who focus on high-grade cards, and these collectors probably don't spend their days digging through listings on eBay. Again, just my 10 cents and perhaps there is something more that I'm missing.