Every lobbyist swarming Capitol Hill these days knows that, when it comes to legislation, the devil is always lurking in the details, not lounging in the concepts. Yet it is concepts, not details, which are drifting down to the public—who will be in for a surprise when they realize that reform is not what they think it is. How these details are hashed out or slipped into a bill at the eleventh hour is crucial to the success or failure of reform. This is the second of series of occasional posts that will look at where the devil lies in key provisions of the health care bill. The entire series is archived here.

One of the great untold stories of health reform has been whether Americans who will soon be required to buy insurance can really come up with the cash to do so—oh dear, that meddlesome “affordability” question, to lapse for a moment into wonk jargon. The crux of any health reform bill is the percentage of income families will be required to spend on coverage, a point drowned out by all the hoopla surrounding the public option. The press has yet to focus on what ordinary people will have to spend.

A table produced by the Center on Budget and Policy Priorities shows some of the financial calculations that should by now have been finding their way into stories produced by the nation’s media. The numbers aren’t pretty. The table shows how much families with different incomes will have to pay for coverage under a proposed bill that combines provisions from the Senate Finance Committee and the Senate HELP (Health, Education, Labor, and Pensions) Committee.

A three-person family with an income at one-and-a-half times the federal poverty level—$27,465—would be required to cough up 4.8 percent of that income, or $1,318, to pay for a policy. Government subsidies would aid with the rest of the cost. A three-person family with an income of $54,930, a bit more than the median income of about $50,000, would pay 10 percent, or $5,493. But if, instead of a merged bill, the one approved by Senate Finance Committee triumphs, the family with the lower income would pay only $1,236; the family with higher-income would pay $6,592, or 12 percent of their income.

Either way, these are hefty amounts for families that don’t have much income to begin with. As blogger Robert Laszewski has noted repeatedly on his blog, Health Care Policy and Marketplace Review, few families with an income of $55,000 have $6,500 or even $5,500 lying around that they can spend on health insurance. If families don’t qualify for hardship exemptions, insurance would compete with money needed for the electric bill, or for gasoline, or for whittling down high-interest credit card balances. “Where will people be if they knew this?” Laszewski asks, arguing that “they need to know that before deciding whether an individual mandate makes sense or not.” So far, the press has not linked the raw numbers to the individual mandate.

But wait! It gets even worse. Fine print buried in the Finance Committee bill threatens more budget stress for already strapped families, especially those with low or moderate incomes. Even if families can afford to spend what Congress decrees, over time they will find themselves paying much more for their coverage—perhaps far more than the 2, 4, 10, or 12 percent that bill drafters have in mind for them right now. Last week, Julie Appleby of Kaiser News Service exposed this little devil lurking in the details. And it’s a doozy. Appleby reported:

The cost of coverage would shift from a percentage of income to a percentage of the premium, no matter how high the premiums go. Because premiums generally rise faster than wages, consumers getting subsidies would pay a larger percentage of their incomes toward premiums over time.

Trudy Lieberman is a fellow at the Center for Advancing Health and a longtime contributing editor to the Columbia Journalism Review. She is the lead writer for The Second Opinion, CJR’s healthcare desk, which is part of our United States Project on the coverage of politics and policy. Follow her on Twitter @Trudy_Lieberman.