I appreciate your point, but it still doesn't address where the Federal Government derives the power to pay for these.
Drugs are expensive for several reasons. The amount of money it takes to bring a drug to market is in the hundreds of millions. Maybe more. They have to cover that expense. This doesn't count the drugs they spend a fortune developing that don't get approved. Those have to be paid for. Finally, they have a limited amount of time to sell their drugs at a premium price because as soon as the patent runs out, the generics are on the shelf. If anyone thinks they are making a ton of money, go invest in Merck or Pfizer and watch your portfolio drop.