The second lowest silver ACA plan for Mrs. C. and me is $23k. That's with a health insurance company hardly anyone has heard of, with an extremely narrow network.
A silver plan has an actuarial value of 70%, so let's say our current healthcare cost is $23/0.7 = $33k.

kff.org - Subsidy calculator

It would totally be worth it to us to get Medicare level coverage for $38k. Where do I sign?

Have you looked at off-marketplace ACA-compliant plans?

The marketplace plans almost invariably have very narrow networks, as insurers try to manage the combination of community rating (why the premium is so low) and subsidies. The marketplace is set up to try to get people cheap health care coverage that has a certain actuarial value - which means insurers try to keep costs down by narrowing the network, which is pretty much the only available route. They typically won't offer their broad multi-state PPO products there.

But many insurers offer those insurance packages through brokers or direct purchase. They're unsubsidized and expensive, and not always available everywhere. But if you're in a place where you can afford to pay the actuarial cost of a broad-network plan, you might be able to get it if working through a broker rather than getting cheaper coverage on the marketplace. I'm curious if that would be available for you.

Needless to say, while that might work for you, when most folks think of Medicare for All they're probably not imagining a $3K per month policy premium. One major reason why the idea of Medicare for All is so popular, but every state that's seriously tried to make it work has been unable to get the dollars to line up.