If you want a sense of just how far-reaching the impact of a Supreme Court decision gutting Obamacare subsidies could prove, new data on health care signups released this week provide a fresh way to game out such a ruling’s consequences.

The Department of Health and Human Services announced the other day that some 11.4 million people have signed up for health plans through federal marketplaces. The new HHS data also provides a breakdown of the number of sign-ups in each of the three dozen states on the federal exchange — precisely the states that would no longer get subsidies if the Court invalidates tax credits to people in all federal exchange states.

This provides a way of approximating just how much money in tax credits each state could lose if the Court rules that way. We’re talking about enormous amounts of money: Florida could lose nearly half a billion dollars per month in subsidies to its constituents. Texas could lose a quarter of a billion dollars per month. North Carolina and Georgia could each lose over one hundred million per month.

Here it is in chart form (a note on methodology is below), detailing the impact of such a ruling on the 14 states that stand to lose the most:

tax credits for GS

The column on the left details the approximate total number of people in each state who qualify for subsidies. The middle column details the average amount in subsidies per person. And the column on the right details the approximate total number of dollars per month that are set to flow into each state — money that would presumably stop flowing if SCOTUS guts the subsidies.

This methodology was suggested to me by Larry Levitt, a senior vice president at the Kaiser Family Foundation who may know more about the Affordable Care Act than anyone else alive. He says one reasonable way of trying to calculate total subsidies per state is to take the total number of new signups in each state, and multiply that by the percentage in each state who qualify for tax credits, data that is also supplied by HHS. That produces the approximate total in each state who qualify for subsidies (the left column).  You then multiply that by HHS data detailing the average monthly subsidy payment in each state (the middle column), and it gives you the approximate total in monthly subsidies to each state (the right hand column).

A few caveats: First, these calculations are very rough and approximate. The data on the percentages who qualify for subsidies and on average monthly subsidies are a little bit older than the newest data on total signups (but they probably won’t change much). Also, not all of the people who signed up will end up paying, so these totals will likely drop somewhat, though it’s hard to know how much. Still, Levitt says this is a good way of trying to gain a rough sense of how much money in each state we’re talking about here.

“This a very reasonable approach to estimating the amount of federal subsidies people living in these states will receive,” Levitt says. “Billions of dollars are flowing to low and middle income people under the law, and most of those are going to people in states using HealthCare.gov. This makes it very tangible: If the Supreme Court sides with the plaintiffs, states would be losing in some cases hundreds of millions in federal money per month.”

If defenders of the law get their way, numbers like these could end up having legal significance. A number of states have argued, in a brief filed for the government’s side, that the plain text of the ACA contains no explicit threat to withdraw subsidies from states that fail to set up exchanges. Thus, they argue, if the Supreme Court guts subsidies, it would impose a “dramatic” hidden punishment on them and their residents for their decision not to set up an exchange, despite the fact that they had no clear warning of the consequences of that decision. This raises serious Constitutional concerns, and as a result, the states argue, the Supreme Court should opt for the interpretation of the statute that doesn’t raise those concerns — the government’s interpretation that subsidies are universal.

This federalism argument, which has been expanded upon by law professors Nicholas Bagley and Abbe Gluck, could potentially appeal to Anthony Kennedy or possibly to John Roberts. The fact that the states stand to lose such enormous amounts in subsidies to their residents could help underscore that case.

Indeed, all of this suggests that a SCOTUS ruling against the ACA could create real problems for GOP lawmakers in many states. Reuters reports that officials in some states are currently scrambling to figure out what to do in the event of such a ruling. Even state officials who want to respond by setting up their own exchanges — keeping subsidies flowing — tell Reuters they may not be able to do so for political and other logistical reasons, meaning they’d lose subsidies even if they don’t want to. In Ohio, for instance, GOP governor John Kasich has suggested he wants to come up with a fix but doesn’t seem clear on what. It’s perhaps not surprising, then, that relatively few red states have signed a brief in support of this lawsuit.

Meanwhile, Republicans in Congress are working hard to convey the impression that they might have a contingency plan in place — or even their own alternative health reform — for those who might lose subsidies and coverage. Such feints are probably just designed to persuade the Justices that the consequences of an anti-ACA ruling might somehow not prove so dire. But, taking those Republicans at their word, numbers such as the above provide a useful way to judge any such contingency plans or alternatives: Do they come anywhere close to covering the same numbers of people?

Conservatives might seize on these sums of money for their own purposes. Some on the right are arguing that, if SCOTUS does gut subsidies to millions, Republicans must not offer a fix that spends anything close to the same amount in subsidizing those people’s health care, and instead must advocate for a return to a pre-Obamacare baseline level of spending and propose “free market” solutions instead. These conservatives will likely argue that such huge expenditures as those detailed above underscore their point.

As I’ve repeatedly written, I think there’s a decent chance the Justices could side with the challengers. The massive amounts of money at stake underscore that if this does happen, a whole new political and policy story will unfold from there, with consequences that no one should pretend to be able to predict.