Amazon.com and Walmart Inc. have both jumped into the online pharmacy market and now Costco Wholesale Corp. is taking a different approach, with a focus on helping make prescription drug prices transparent for employers. It has partnered with Navitus Health Solutions LLC, a small pharmacy benefit manager (PBM) which has a different business model than most PBMs. Rather than taking a cut of rebates and discounts, they charge a flat free. Costo recently purchased a minority stake in Navitus in a partnership which should benefit both employers and consumers.