Funny that i logged on today and saw your post.
Working on this issue with friend on the left coast.
"In an article in the January 2013 issue of Costco Connection magazine, the club warehouse retailer is promoting the new PBM, Costco Health Solutions, to small business owners. Pharmaceutical industry consultant Adam Fein noted on his blog, Drug Channels, that Costco was seeking to emulate the tactics already used by CVS Caremark, Walgreens and Walmart to drive prescription growth."
The program I learned about yesterday works with TPAs in their offerings. This gives them more economies of scale.
Most PBM programs offer a percentage of savings while keeping part for themselves. This company I was introduced to uses a different method. They charge a PEPM fee and pass 100% back to the employer on the ERISA
They include COSTCO and the others you spoke about.
I would be happy to speak to you about it, if you have some TPAs that might be interested.