[jsfriedm]

I think a key part of the phenomenon of a previously underappreciated player gaining in popularity/value is potential constituency, and the most ready-made constituency for such a move is the team fan-base. If a previously down team starts to win for a prolonged period, especially if that coincides with a period of economic and demographic growth for their city, the fan base grows and that could lead to the appreciation of the team's vintage heroes (think Atlanta, Houston, etc.). On the other hand, if a fan base shrinks, there are fewer people who might be inclined to re-discover that team's heroes (I don't think it's a coincidence that so many of the top candidates for underappreciated players are Philadelphia As - Eddie Collins, Jimmie Foxx, Lefty Grove.)