Plan A free
Plan B 170 if MAGI < 182K
Plan C most people don't buy it
Plan D normal plan premium if MAG < 182.
Normal plan preimium is about < $100 per month, with annual deductible around $500.
So if you MAGI < 182K (for couple), your medicare monthly cost is around $300.
https://www.valuepenguin.com/medicare-cost
https://www.medicare.gov/your-medicare-costs/part-b-costs
https://www.nerdwallet.com/article/insurance/medicare/how-much-does-medicare-part-d-cost