They sure are undervalued. Great from a collector perspective, though.
It's the nature of the game. It's such a unique sport. The QB gets all the limelight, then WR, RB's and after that it's pretty much all f the rest that are undervalued even though some positions are crucial to a team's success - like linebackers and tackles that can rush like Donald.
Someone collecting a Center heavily would be cool to see.
I'd also like to see someone collect a long snapper - provided they have cards.