Risk adjustment payments are not subsidies. They are monetary transfers from some insurance companies to other insurance companies. They cost the government nothing. Well, maybe a little bit of administrative cost, but basically nothing.
I think in economic terms they are cross-subsidies. Companies with risk profiles that are lower than expected make compensating payments to companies with higher than expected risk profiles, with the result that the low-risk people insured by the former group are charged more than the company’s actual risk pool would justify in order to fund the payment to the latter group.
That’s true on all sides (and don’t forget the lawyers).