Worthpoint has an interesting article on factors that affect the value of a collectible and why many go down after a while. Certainly a timely article in light of what's happened to collectible casino chip prices.

In particular, read
6. Ouch! Maybe You Just Paid Too Much .

http://www.worthpoint.com/blog-entry/when-collections-lose-value-why-some-collectibles-dont-hold-their-prices?utm_campaign=561&utm_medium=email&utm_source=phplist