^this. In my case, pre-ACA as an early retiree with no medical issues, I was able to get a catastrophic plan for under $100/month with a $4000 annual deductible. Nice deal!
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ETA: and with nothing in the ACA to contain premium cost increases over the years, and having a "captive" group of people who "must" buy health insurance, the odds are that premiums will rise each year at (perhaps) a greater rate then they did before health insurance was mandatory.
Catastrophic plans are still available, generally for around $100/month (but with free preventive care and they now have real legit coverage with no coverage limits once you hit the deductible). If you're under 30 they are easy to get. If you're over 30 you can ask for an exception to get them.
The ACA does have some things to limit costs--not nearly as much as would be ideal, but it's still there. Insurers have to spend at least 85% of premiums on medical care (limits the amount going to overhead, profits, executive pay, etc). That lowers premiums. The Marketplace is now competitive so you can make apples-to-apples comparisons between plans, selecting based on price, benefit structure, and network, since essential health benefits are required for all plans. This drives the cost of plans down. There are all kinds of things that are trying to change the system from "we get paid to do stuff to you when you're sick" to "we get paid to keep you healthy" like accountable care organizations that get paid more when you are taken care of and stay healthier and less when they don't do a good job at coordinating care and you get sick. This lowers healthcare expenditures. These are just examples. Almost no one in the general public knows what's really in the bill because it's absurdly complicated and there are so many simple lies that have been repeated ad nauseum.
The US healthcare system is a pretty ridiculous way to do things. The ACA's biggest shortcoming is that it leaves things the way they are for the most part, while only making some things better (at the cost of penalizing some people for not getting insurance).
Free markets are frequently a great way to run things. But healthcare never was and never could be a free market because too many aspects of it violate the fundamental assumptions of free market economics. For example, there is almost no pricing transparency. It's almost impossible to figure out what a healthcare service will actually cost you before you get it. Even if you're in the business and know what you're doing, the numbers you get can literally be $1000s different from the real bill. And pricing varies wildly without any relation to quality (studies show literally no correlation between cost and quality of care). One provider near me quoted $18k for a colonoscopy, and another quoted $600. They were both 3 miles from my house. That's like Kroger charging $18 for milk and Walmart charging $0.60. It's the same milk. Another example is information asymmetry. There is no way that you can know as much as your doctor about the medical care they are providing or recommending for you to get. You simply have no way of making a fully informed decision whether the recommended service is worth the cost (in time, money, side effects, etc), and especially in comparison to another variety of service (with the provider may not even have suggested to you as an alternative).
Anyway, the system is terribly broken and the ACA fixes some of it. I'm hopeful additional fixes will come soon, but they likely will not be coming through legislation.