Yeah, I think I recall BGinGA saying something like you'd need to be ordering in excess of 100,000 chips via CPC to see any cost reduction. And it'd be tough to put a GB together because the costs are still going to be significantly higher than something like the China Clays we got for a quarter each, so it really reduces the volume of folks that can afford it, and the volume of chips they can afford to purchase.
If we struggled to get 300K chips $0.25 each, I think we'd struggle to get a third of that quantity made when the cost is going to be something like 6+ times more per chip even with a group discount (and don't even get started on the back and forth bickering between members on color choices, spot patterns, inlay designs, etc)
I had asked a similar question. Plus, at the end of the day having your own custom set that people know is YOURS is kinda cool. Just don't forget to calculate samples into the mix, people WILL want sample sets of your customs!