How could that be? The details are complicated, but the crux is that insurers and state regulators worked together to find a way to funnel more federal money into the Obamacare insurance markets.

The insurer-regulator hack will mean that navigating the Obamacare marketplace will be more complicated for consumers (more on that later). And the change will cost taxpayers more money — perhaps $21 billion more in 2018 alone. But, in the end, most customers will be unharmed by the president’s decision, and a substantial fraction will be better off, able to buy plans for about the same price they pay now, yet with lower deductibles.

The president’s move was to cut off a form of Obamacare funding known as the cost-sharing reduction subsidies. Those were payments the government made to health insurers to compensate them for lowering the deductibles and co-payments for low-income customers.

But he didn’t cut off another, more important form of subsidy. The Affordable Care Act also includes tax credits that help low- and middle-income Americans pay their insurance premiums. Those tax credits increase in value along with the price of a certain midlevel insurance plan, known as silver. If you qualify for a subsidy, you can never be asked to pay more for that plan than a set fraction of your income.

Insurers in more than 40 states have decided to compensate for the missing cost-sharing subsidies by making hefty increases to the prices of this silver plan — but small or no increases to their other plans. Consumers who qualify for subsidies are still asked to pay the same fraction of their income toward a health plan, and the federal government pays the insurers the rest of the higher silver-plan premium. So consumers are no worse off, and insurers make up for the loss of the cost-sharing subsidies canceled by Mr. Trump.