For Walmart, it's a little bit more complicated than just driving customers. That's what you see in retail. Wal-Mart also is a wholesaler in the pharmacy sense. One of the matters that drive acquisition costs from PhRMA are the pricing bands from the insurances you take as part of the contract with PhRMA.
Easier to give an explained example:
Lisinopril 10 mg for 1 tab:
AWP or WAS (whatever fictitious number is used): 0.50
Blue Cross MAC: $0.10
Caremark MAC: $0.08
Lord999s Krazy Kard MAC: $0.30
Realistically, the MAC should be around the mean of the legitimate plans (0.09 although in actual practice, the harmonic mean with patient count as the denominator is used), but with the Krazy Kard, it's at an inflated $0.16.
Here's how everyone but the patient wins:
Krazy Kard gets some sweet love from IMGHealth and marketers to the poor and stupid because I have the suckers' demographic data who used my cards and their probable health condition. A simple HIPAA business associate agreement later, and Mr. Anderson's Lisinopril, his physician, and the demographic data I got from him signing up is now in the hands of insurance companies and marketers.
Wal-Mart makes three postives: people in the door as mentioned, the opportunity to fleece customers by charging above reimbursement rates paid in cash who would be greatful, and the opportunity to inflate their MAC to insurance companies to demand better reimbursement terms. "Blue Cross, I have this company that pays three times your MAC so either raise your rates or we're walking. No liability either for the fleecing, after all, it's a discount card.
Same thing for PhRMA and aggregators. Easier to buy data from small fry than Blue Cross, so divide and concur (intentional spelling) is their gain.
The easiest analogy to relate is try to go into Kohls and buy anything at full price. There's a coupon for anything at 15% off, so what's really going on? It's that number games and creative accounting intentionally obfuscate third parties from knowing your business, a time honored tradition in pharmacy.
Industry will happily give indigent patients free Meds from their supply in exchange for positive outcomes data to argue with regulators and insurance, loss of privacy, and a tax writeoff. That's more valuable in small quantities than selling the drug. God bless America for figuring out a way to turn anything into an opportunity.