I want to reset your scenario a little, if I may…
People currently purchase (either on their own, or thru their employer) a health insurance policy. They are purchasing access to the network of providers and hospitals the insurance company has negotiated with for set, discounted rates on services provided. If you do not have a policy with an insurance company, then you will likely pay a lot more for accessing services (or nothing, if you don’t have the money and do have a medical emergency – the cost is passed on to everyone else). If you use a provider not in the insurance company’s network, you will also pay more than using their network. Your choices are usually limited to what your company purchased thru group insurance, but you are free to decline that and go ahead and purchase your own individual policy (which will probably cost you more). If you do not have a job, or are poor, the current system does not really provide health insurance for you – if you are unemployed and have a medical emergency, you need to become poor (by draining your bank account) in order to access state-sponsored health care (like Medicaid).
The customers of an insurance company are called a risk pool. They want a large pool of people that spreads out the risk – some people may be sickly and cost more, while others may be healthy and continue to pay their premiums. This is why it is called “Insurance” - healthy people buy insurance “Just in case” something happens to them. If the risk pool has a few sick, expensive people, and a lot of healthy people who do not access services very often, then the model works. Competition keeps the insurance companies from ratcheting up rates too much, as well as regulations. Old, expensive people do not have to participate in this game because they are covered by Medicare, so this relieves the insurance companies from having to cover them.
The insurance company does not usually decide what to pay on a case-by-case basis – they disclose to you what they will cover and how much you will have to pay for specific services at the time you sign-up (but it seems most people do not ever read their policy). Insurance companies generally do not try to limit their payouts – they will meet their obligations agreed to in the policy. Many of them have been caught doing unscrupulous things to affect their payouts – but have been caught and paid sizable penalties – there is not a big incentive to cheat their own customers, although that perception exists. If you want a better policy that covers more stuff, you are free to purchase one, but it will cost you more.
The current system is in a run-away cost structure that is unsustainable. The costs the insurance companies are charging is based on them making some profit, but is also due of out-of control doctor and hospital costs, as well as expensive drug treatments.
The Affordable Care Act (AKA Obamacare – yes, they ARE the same thing), was developed to try to curtail the runaway costs, and ensure most everyone has access to health care by making everyone purchase insurance. One key aspect is that insurance companies can no longer turn away sick people, or people with pre-existing conditions, but for them to be able to accept this, they need to increase the risk pool (spreading the risk) – this is why there is an individual mandate for everyone to purchase health insurance.
In theory, the ACA will (eventually) end up costing less than the current system because uninsured people will not keep mooching off the current system whereby their health issues are foisted onto the insured (and increasing costs – in theory, healthy people will cost less). If everyone SHOULD be insured this way is a philosophical question.
I think where you are coming from is if all the subsidies being offered to the poor are going to end up costing more than the system brings in. I think it remains to be seen how that will work out. I will point out that there are other government programs that give out more than they take in, but in those the benefits are percieved to outweigh the costs.