So... how do you value a card...

[TanksAndSpartans]

I'm on 4SC mailing lists and they do run weekly sales - usually around 10% off and usually on something specific like PSA 10 cards..... Although in this case, it seems like your instinct is this card wouldn't sell at auction for this price, so if you're like me me and you pay a high BIN and then it gets auctioned off later for less, you'll wind up kicking yourself.

Jeff's point was good about finding an analogy if you cannot find price data on the same card in the same grade. Maybe find another HOF lineman PSA 10 from the 70s.... Maybe Gene Upshaw or John Hannah PSA 10 cards?

I don't think using a factor will work - I do that sometimes if say I just missed on a PSA 5 and then a PSA 6 comes up - I may multiply by 1.25 or something, but I think that only works for the section of data that is somewhat "linear". The PSA 10 cards are sometimes off the chart compared to the other grades - Rickey Henderson in baseball comes to mind.