[cjedmonton]

Great insight/feedback so far!

In my OP, I acknowledge that the promoter's cut has taken a steep climb, but that can't be the only factor to explain the jump over the years.

Surely, the athlete is privvy to the value of his signature and charges accordingly. They are also well aware of the opportunists whose main focus is to flip the signed item for a quick profit. I recall reading somewhere that many athletes build in a certain amount for "deterrent" in their fees so as to make it more difficult for someone to profit from their signature. If that is even partially true, I couldn't imagine what Mantle/DiMaggio/Williams would charge in 2013.

Either way, this is not easily proven/disproven. I was just interested in the overall trend over the years, rather than a year-by-year recap of prices from a single promoter.