Wrong.
"I̶n̶ 2̶0̶2̶3̶ a̶l̶o̶n̶e̶, t̶h̶e̶ f̶o̶u̶r̶ b̶i̶g̶g̶e̶s̶t̶ i̶n̶s̶u̶r̶a̶n̶c̶e̶ c̶o̶m̶p̶a̶n̶i̶e̶s̶ i̶n̶ t̶h̶e̶ U̶.S̶. p̶a̶i̶d̶ a̶ t̶o̶t̶a̶l̶ o̶f̶ $̶3̶.7̶ b̶i̶l̶l̶i̶o̶n̶ t̶o̶ g̶e̶t̶ t̶h̶e̶i̶r̶ n̶a̶m̶e̶s̶ o̶n̶ y̶o̶u̶r̶ s̶c̶r̶e̶e̶n̶s̶" [1] (EDIT: It's less than $30bn [3].) out of $1.5 trillion of premiums collected [2].
[1] https://www.bankrate.com/insurance/car/insurance-advertising...
[2] https://www.cms.gov/files/document/highlights.pdf
[3] https://www.emarketer.com/content/us-healthcare-pharma-ad-sp...
2. I misspoke and meant "marketing" broadly, not ads in particular. This all fits under administrative overhead which is one of the major sources of inefficiency between private health plans in the US compared to Medicare/Medicaid.
Do you have a figure for this?
They are both insurance programs.
Aside from variations in fraud detection efforts (which Medicare/Medicaid should do more of), what justifies such a gap?
It's various methods by which they grow and retain market share, which Medicare/Medicaid don't need to do.
This doesn't say the difference is in marketing.