[pudge27t]

IMO its a case by case scenario per player. As for me Reggie's market goes up and down depending on his fan base. So I'd like to hear from someone who collects Aaron Rodgers or Tom Brady to get a "better" or consistent answer! :p
But for me that rough 35%-50% range you mentioned is a good starting point, yet IMO should be used as a "guide" like bojesphob stated & should not be "engraved in stone" like a lot of people think it is.

Many variables come to mind as well.
RCs - A lot of people collect just their RCs or like in my case, when a player joins the team, collectors snatch their RCs until the player has a released team card. (Major market jump)
Set Builders - No so much for me anymore but i know stuff like the new RPAs out of Immaculate or Black Gold, everyone is trying to snatch them up!
Injuries - I know when Tom Brady got hurt years ago, everyone was dumping their stuff! I got lucky and snagged a Contenders AUTO RC for $300, its gone now though.
Teamless - A player with no team. As I learned as of late, a lot of people were dumping Reggie's out onto the market making it easier to get those that I wanted/needed! FINALLY!
I also found out this can somewhat drive prices up on certain rare cards as some sellers choose to hold on to a card until the player goes to another team. Yet for "the right price" it can be had. :p