Where we are at the broker got paid for selling the supplemental plans as well. Our broker didn't really care whether we chose an advantage or supplemental plan.
There wasn't a commission on the Part D (drug plan) so we did have to handle that piece.
I believe you'll find that most independent brokers collect their fees from the insurance company with no additional charges to the customer, They get compensated by all the companies equally so they should have every incentive to put you in the best plan for you.
From the National Counsel On Aging
Find an independent medicare insurance broker that's local to you and get them to explain the benefits of both the advantage plans and a medicare supplement plans.
Ask your over 65 friends for broker recommendations.