The $1M/year cost will ensure the tiniest percentage of the top 1% will have access.
First of all, if the treatments are simple enough, there will be a ton of third world countries doing it in cheap clinics and the US won't be able to stop it. Imagine trying to pressure China or India into discontinuing such services.
Second, it is advantageous for the billionaires to collect massive data on safety and efficiency of such treatments before testing them themselves, and data on mice are almost irrelevant here; for such profound treatments, you need to know how they work in people, and your dataset needs to be huge, because people are a pretty diverse lot.
Third, all developed countries struggle with aging populations. In order to keep their economies afloat, they need to be able to reduce impacts of aging across the board, not just in a few privileged people.
How much has the cost of a heart transplant gone down since its invention in 1967?
Realistically though, we have a pretty good idea of what we're looking for. We don't know the exact combination of chemicals that cures aging, but we know it's going to be a combination of chemicals, and we know we can mass produce those.
I get a med that's $18k every three months, for a mililiter of fluid. I wouldn't have a hope of paying for that without health insurance, and I'd expect health insurers to be resistant to covering mega-expensive life extension therapies.
Generally, the more common diseases are cheaper to treat, because the burden of development, IP etc. gets spread across more people.
Medications for ubiquitous stuff such as high blood pressure tend to be comparably cheap, unless they are a fresh novelty. And aging is even more widespread than HBP.
Estimated at 2-3% of the world population, so 100M+ people.
I am sorry to be prying such information out of you, but things with such a cost label tend to be very high-tech (e.g. tumor-invading lymphocytes etc. that need to be cultivated for each patient separately, which cannot possibly be cheap).
I suspect it'll look cheap in comparison to life extension treatments.