Moonlight Graham-Why isn't he worth more?

[Moonlight Graham]

Ok, I have been dying to ask you, the Net 54 experts, who's opinions I respect, why aren't Moonlight Graham's few baseball cards worth more? I consigned a 1902 cabinet card of the Charlotte Hornets Base Ball Club with Archie "Moonlight" Graham in it (his rookie card you could say), and it was graded by SGC as a 20, to this year's Robert Edwards Auction, and it only sold for 1500. I believe last year a pretty beat up picture sold for around 1900-2000 in the same auction so I figured my piece would do a heck of a lot better than that. I've been afraid to ask this question because of the answers that I might get. I know Moonlight is famous because of the movie "Field Of Dreams", but he does have a great story as well as a great nickname. On Ebay, I have listed a couple of Moonlight pieces that I own at really high prices just to see if there would be any serious interest out there, but there isn't. I know my crazy prices had something to do with it, but I really was hoping to just gauge a value and not sell them. If I would have known that my cabinet would only sell for 1500, I would have kept it. Anyway, I love the movie and Moonlight's cards so I guess that is all that really matters, but at the same time it's always cool to know that you own something valuable too. Then again, that's not what this hobby is always about. Thank you in advance for all of your comments and insight!!!