Both major chip catalogs tie their values to dealer prices; what you might pay a dealer at a show or by mail. Not many dealers will agree to sell you a chip for less than $2 over their cost.

My rough formula for retail value of chips currently available from a casino is:

Price = $2 + (120% of face value), rounded down to the nearest dollar. The percent of face adder helps take into account the cost of tying up the dealer's money for an undetermined amount of time.

This formula doesn't apply to limited edition chips a few years old, as these generally sell like commemorative postage stamps... below face as the dealers mostly have way more than the hobby demands.

The above also doesn't apply if the chips are from Hard Rock Casino in Las Vegas. I've never been able to figure how collectors get the values they pay for these [g].

When you are talking trading chips between collectors, you are talking a different set of values. A lot depends on how well the traders know one another, how motivated they are to trade, and the number of chips required from each trader. The $2 markup still is in the back of most traders minds and most won't trade you a $5 face value chip for 5 $1 face value chips.