Where are you located? I know Florida has high premiums for Med Supp, but not every state is like Florida. I don't see such high premiums for Med Supps here in Georgia. At least not until they are much older. An 80 year old male can get a Plan G for $157.34 in my area (female $136.74).
I don't disagree with your analysis. A healthy person could definitely save money in a normal year on a Medicare Advantage plan compared to a Med Supp. But there are other factors involved. The biggest one being whether or not their doctor is in the network. Or the hospital they prefer. I find many seniors don't like restrictions of any kind. And some like knowing their worst case scenario is their Med Supp premium.
For the most part, my MA client base consists of those who just can't afford a Med Supp. However, I do have some who have the means but still choose a MA plan. And that's fine too. I will help them either way.
I am in Florida and between Aetna, UHC and Humana, most doctors here are in at least one of the networks, so that is usually not a problem. The cost and risk are not the only considerations in Florida. We have may people who spend part of the year down here and part of the year up north where they came from. "Snowbirds" I usually recommend a supp for them. If they have two homes, they can usually afford a supp, and they don't have to worry about networks.