You do realize not every location has $99 Plan G rates, right? I just wrote a T65 yesterday who lives in my same city, rate is $147. Now if his wife goes with the same carrier when she turns 65, his rate will decrease. But this particular carrier still pays the commission on $147. That's $370 x 6 = $2,220. Add in the PDP and it's a minimum of another $342 over 6 years. This adds up to more than MAPD over the same 6 years.
that was plan N for a Male. Plan N rates will be more stable Plan G $139 but there are cheaper rates but this is with one of the bigger carriers.