Allan,
As always you make a lot of good points about pricing.
Your point on about 50 people to have "Z" chips is probably very true, and once they have them, what do you look at.

I think that eBAy needs to be considered in your structure more so than the other little auctions for that very reason. I searched and found over 1500 chips for sale this week using "CASINO CHIP*" as the search parameters. Doing it for the completed Auctions you find over 3000. Using the sorting features of eBay and selecting bid price and descending value, I think those with say 10 or more bids show active, honest , market pricing, Many chips have over 20 - 25 bids on them; if the seller started them out as a true low auction prices.

The only p[roblem is, it would take a several hours a week to analize this data, but putting some parameters like the above selection it might shorten the process.

I am sure what ever you come up with will be unbiased, and the fairest around.
JIM