It's calculated that under the current system, insurance for an over-65 would be at least $30k annually. And healthcare costs have been rising 5 X as quickly as wages, so that's not the end of it. You and Andy might have no trouble building up an extra mill or two to cover your healthcare needs in retirement, but many others would struggle.

The only way to hold down costs is to include as many healthy people as you can in the insurance pool so you can use the surpluses from healthy members to help pay the costs of others. Medicare effectively does this by sharing its costs across most of the community. The insurers don't do this- they risk-shunt, trying to gather healthy customers to themselves and pushing sick or risky people elsewhere. That's the main form of "competition" between insurers, because it allows them to extract surpluses as profit rather than to cover care for people as they age or get sick and need care. So you'd need to legislate to prevent this sort of discrimination and as soon as you do that, you need individual mandate as well so people don't check in and out of insurance to cover healthcare needs as they occur.