These 'services'- AMEX, Costco, etc are all simply an agreement with the dealership to allow a few cars to be sold at 'internet pricing' discounts.

Talking to two different sales managers, they will have some models "on" the program, but others not. Basically if they are offering 'deals' via the usual channels, they offer the same deals via these services. And likewise, a hot car, in high demand, where no one is dealing, will not be offered at silly discounts via AMEX, etc

A