I can agree and disagree, first what is "Rare" And I do not mean as discribed in James Campiglia's book, as many do not have his book. A $1.00 harrah's yellow brass may be rare to someone who lives on the East Coast, but to someone one who lives in Reno, the chips are still in use on the crap tables at Harrah's.
In fact right now there is a chip on e-bay by a very respectted seller, who states the chip has never been on e-bay, and the current bid is near $1,000. Maybe his chip has never been on E-bay one one like it Sold on E-bay last December for $525. It is the buyers responsibility to know the value of a chip before buying it, would anyone buy a house just because the seller said it is worth X amount?