In the United StatesMedicare part D plans is a plan purposely to subsidize the costs of prescription drugs for beneficiaries. There are various categories under Medicare Plan Part D to cover certain drugs. There are tiers that a beneficiary has a set copay amount.Tier 1 might have a copay of $5–10 per prescription. Tier 2 copay of $20–$30, could be around $40–$100. Tiers 4 and Tier 4 is the highest and more expensive.