"[The delay] is great news for plan sponsors, who seemed unable to obtain contract provisions from third-party administrators (TPAs) that stated the TPA would comply with these rules.... [P]laintiffs' lawyers [may] use this information as the basis to bring lawsuits claiming that plans are overcharging participants for healthcare coverage.... [H]ow drugs are priced remains in a black box for most employers. This information would allow an employer to compare what its health plan paid for prescription drugs against another employer health plan."