Just curious. They usually sell what they have at book price or below and often there is a tax to be paid on the purchase so they have to lower their prices even more for a client to want to buy. They must buy their notes and coins very cheap to make a profit... but how?
I understand all the multi-color and birds they got are probably kept from circulation, but the 1954's and older, dominion, chartered banks', etc? Is there some kind of whole sale?
They way I see it, if the number of collectors increase, all old notes will eventually be kept in someone's closet and become impossible to be found.
Already the highly priced 1935's and $4 bills and such are hard to find. You'd have to make special requests to a big collector and in spite of the high prices you'd be lucky if he's whilling to sell. If he is, he'll over-grade knowing that you want the bill badly. All "Buy it now"'s on eBay are ridiculously higher than book value. Heck, I've been collecting for 15 years now (mostly buying) and if someone offered me full book value for my entire collection, I would still not sell !
Either that, or, paper money becomes an old fad like Pokemon cards