Plan "N" does not cover "Medicare Part B excess charges". 
It is my understanding that this pertains to a situation where the doctor would charge more than the Medicare approved amount. The patient would be responsible for any difference.  Correct me if wrong. 

It appears that this creates what it is technically an unlimited cost exposure for a patient. But realistically, Does this happen often? 
Since every medical establishment claims to be loosing money is this a greater risk in the future?
Is it worth $500 extra per yr to go to "Plan G" and make this potential cost risk go away?
I have heard that "G" might not have a long future. Get it while it's still available?
Any insight is appreciated.
THX