[red-indian]

"Is there any reason not to make discounted rates for insurers illegal?"

Flat pricing for all is possible and workable under single-payer.

[kelnos]

I'm in favor of single payer, but single payer is not required for this. Requiring all prices to be published, and simply passing legislation to make discounted rates illegal, should do it. (Sure, there are probably ways to game that system, but ideally there are also ways to catch worst offenders and punish them with fines to the tune of several multiples of the discount.)

[ivalm]

It's also probably doable as a law (which is to say a law that states that healthcare org must sell services using a fixed price list, which the org determines beforehand).