The overall cost is negative because healthcare spending is $2.6T less than where it would be without the ACA. By repealing ACA, you are advocating the increasing of healthcare costs and increasing the deficit.
The ACA contains both savings and taxes. The taxes don't apply to people that are not high income, meaning that they are not a cost for anyone but rich people. So you want to explode healthcare spending to unsustainable rates, as before the ACA, despite your phony concerns, remove the cost control measures that have brought healthcare inflation to a record low, kick 30M off healthcare insurance so that they can go broke or die if they get sick, in order to give a tax cut to the rich.
The exchanges are not faltering,
enrollments are at record highs. You've shown no examples, so that makes you a liar. Like when you linked to an article insinuating healthcare inflation is out of control when in fact it's at record lows, which was another lie. Your claim that ACA made the healthcare spending problem worse when in fact it has made it better, also a lie.
Until you put down the ideology, stop ignoring the debunking of your nonsense, and get with the facts, you cannot be helped.
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It doesn't favor insurance companies because ACA regulates the % of premiums that insurers must pay out for healthcare (60% to 90% depending on plan type). This effectively caps the profit margin from health policies (they can still squeeze profits from other non-policy related areas like administration).
Getting insurance on the same day you need it would bankrupt insurance companies, but would not bankrupt the government. That's why single payer systems work in every other advanced country, providing more coverage than the US, at cheaper prices, and with better health outcomes (it's effectively a free lunch).