What is wrong with medicare.gov??

When viewing the Plan Results for prescription drug plans on the Medicare.gov plan finder tool, a list of plans is displayed. When a plan is selected, and the "Drug Costs & Coverage" tab is selected, there is a section titled "What you Pay." This section includes the selected drugs, the "Full Cost of Drug", Refill Frequency, Initial Coverage Level, Coverage Gap, and Catastrophic coverage amounts for the selected plan. If I then choose a different plan with the same pharmacy and view the "What You Pay" section, the Full Cost of Drug amounts are different. How does Medicare determine the "Full Cost of Drug"? Where do these numbers come from?

If I were an insurance company, I would be screaming since insurance plans that have lower drug cost prices will have lower annual costs even if the plan has lower premiums and/or deductibles.

And if I were a small pharmacy, I would be screaming since I would be losing business since medicare.gov is favoring the big pharmacies.

Why are not all plans rated with the identical drug pricing??