I have always assumed the Negro League market was so strong because of the limited supply compared to demand. For example, the most recent REA auction featured some 1700+ lots and a quick "Negro League" search in the description category turned up 30 lots, only about 20 or less that could be considered true period pieces. That is barely 1% of what most consider one the largest and best major sport auctions.
P.S. Welcome back, and spare the rod if you find my answer unsatisfactory.
