As far as I can tell, there are three kinds of "new customers" coming up:
(1) Those who never could get coverage
(2) Those who don't have it but want it, because they are part-timers or something
(3) Those who don't want it because they are young, or whatever
There's a subsidy available that's indexed to income to help pay for (1) and (2); presumably many of those in (3) will opt to pay the penalty, which should offset the subsidies somewhat.
Here's a good summary:
http://www.washingtonpost.com/blogs/wonkblog/wp/2012/06/24/11-facts-about-the-affordable-care-act/
But I guess your original question -- is $600/mo for a family of 4 realistic -- and I'd have to say yes, I think that might even be what's known as "cheap" :-)
It's a little complicated, but for the specific example of family-of-four and $75k/yr income, I think the cap is 9.5%? That's where the $7125 number comes from. But again: there are some tax breaks thrown in (all the way up to 400% above the poverty line) to lower that number in net. The final details are here:
http://www.gpo.gov/fdsys/pkg/FR-2012-05-23/pdf/2012-12421.pdf
... although they are not exactly "light" reading :-)
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There's a whole aspect to "health insurance" pricing in the US that I figured out a few years ago that's really lousy. Here's the deal: deductibles REALLY matter. Deductibles sound scary, because it's money you have to come up with ... but they know this and play on your fear, so that lower deductibles cost more than they cover. That is, if you want to move from a $1000/yr deductible to a $500/yr deductible, it'll cost you *more than $500* in premium charges. In the "best" case where you actually meet your deductible, you're then paying more in total (premium + deductible) than you would with a higher deductible. And of course if you *don't* meet your deductible, you're saving even more. Basically people who are insecure about their need for insurance will wind up paying more than they need to.
Those of you out there who are in charge of your own insurance, check with your plan to see what the difference in price is if you raise your deductible. It made a big difference for me. Basically for every year you don't meet your dedictible, you're banking a discount; and in the years where you meet your deductible, you're still getting at least a small discount.
When I first found out about this, my deductible was $500/yr. The $1000/yr plan was $625 cheaper. In a case where I had $500 of out-of-pocket expenses, I was saving $625; in a case where I had $1000 of out-of-pocket (or more!), I was still saving $125 ($625 - the additional $500). And get this: it gets even better at higher deductibles.
/jordan