Sort of. This is true if everyone is required to participate in the system. And there’s only one provider. If you imagine there being a cheap plan and an expensive plan, you would probably expect that the expensive plan is a way better return on the dollar because there are fewer poor people on it weighing it down (because poor people are likely to have more health issues).

True meaning it averages out to a reasonably healthy person

>you would probably expect that the expensive plan is a way better return on the dollar because there are fewer poor people on it weighing it down

It is unfortunately true in the US (probably everywhere) there is worse health/higher incidences of chronic conditions in the poor (mostly because all chronic conditions are diet related). However, in the US the biggest weight would be the elderly who have chronic conditions at a higher rate than any other demographic (generally due to a lifetime of poor diet combined with irregular care over their life to treat the conditions until they are Medicare), but thats the irony these are the people already covered by Government healthcare (and they seem fairly happy with it. Its time to extend it to everyone.