Skybolt's raised some excellent points...my only counter would be that for the very tough books, grade is sometimes almost irrelevant (unless it's a xeroxed cover or something). I'd be interested in a copy of Blood is the Harvest, for example, in just about any grade. Or All Negro #1. You can't be picky when there's only a couple dozen floating around in the whole wide world.
And just my two cents, but IMO the sign of a true collectible is when grade becomes a surprisingly minor factor in the desirability and/or purchase price. There was a beater of 'Tec #1 on ebay awhile back that went for big bucks. To me, it's things like that that are the "real" collectibles. I guess the same would be true for OA, though that's not a sandbox I play in very much.
If another first folio of Shakespeare's plays were to pop up, I don't think anyone would give a rat's butt about quality of production or page gloss, know what I'm saying?