ABE is huge...over 50 million books the last time I noticed. Much less selective than eBay. I check both places when I'm looking for a book, or pricing one to sell. Some titles are much cheaper on ABE than eBay, some the other way around. I think many/most eBay buyers are not aware of ABE. I've seen books sell on eBay for several times what they are available for on ABE. Don't believe all of the highest prices on ABE; much of that is wishful thinking. In general, on high end books, stuff sells on eBay for maybe a third of what the top price is on ABE, condition etc being the same. But there are exceptions, where a really choice item in high demand sells for more on eBay than on ABE. What does it all mean? Damned if I know.