> The US passed laws meant to limit marketing and overhead that tied insurers economics to the size of the overall medical bill... which means as healthcare spending rises, the dollars they’re allowed to retain can rise too, which basically means they're incentivized to drive costs up rather than down.

Yes, this is an important piece of the puzzle. The "medical loss ratio" for large insurers (the kind we all know and love) is set to 85%. So they can keep up to 15% of their revenue as profit.

As you said, if total spending goes up, they get 15% of a larger number.