If you are paying a premium for a heretofore "unconfirmed" T206, you're not taking into account all of the Fac. 25, SC backed Sullivan portraits that go completely unnoticed in every day collections. I guess you can extrapolate some measure of rarity -- and if you're a "completist" then you need to have it. But, gosh... I wouldn't pay more than $15 for this card:
http://www.sterlingsportsauctions.co...-*UnConfirmed*
Collect what you love, by all means, but I can't escape the notion that there is something truly illogical about this particular endeavor. Stated another way, if SC Fac 25 Sullivan portraits like this are worth hundreds of dollars, I'm betting a lot more of them get found in the future.