Normally when the government wants to buy something, it asks companies how much they can provide and to name their price. Winners are selected from the lowest bid up until the government has what it needs at the lowest possible cost, and thereby finds competitive equilibrium prices.
Under Medicare’s highly unusual version of competitive bidding, it will pay the winners the median price of all the winning bids, rather than using the clearing price. Bids are also for some reason nonbinding.
This matters because it creates incentives for unscrupulous third-party companies to make low-ball “suicide bids.” If the median price shakes out high enough, they automatically win the contract, buy the medical products from manufacturers and turn a profit. If it isn’t, they can dump the contract since bidding involves no commitment.