两人MAGI 18万以下，都是一个月付170元 plan B

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