So far 28 states, including D.C., have signed on the Obamacare Medicaid expansion. A new report from PricewaterhouseCoopers finds that some hospitals are raking in huge profits because of it. As The Nation reports:

In the 27 states that have accepted the Medicaid expansion, hospitals' profits are climbing while more patients are getting access to care. Some large hospital chains say the Medicaid expansion alone has already added tens of millions of dollars to their bottom lines, and they're expecting to make even more money as enrollment continues.

But in states that haven't signed on to the expansion, hospitals are in a bind—they're getting the bad parts of Obamacare without the good. …

Together, the states that haven't accepted the Medicaid expansion are foregoing more than $420 billion in federal funding between now and 2014, according to PwC, while leaving more than 6 million people uninsured.

At the same time, hospital chains in those states will lose out not just on newly insured customers, but also on nearly $170 billion in enhanced Medicaid payments tied to the expansion.

Hospitals always knew they stood to make money as the Affordable Care Act expanded health insurance coverage, particularly through Medicaid. The fundamental reasons are simple enough: Hospitals have to care for everyone who comes in the door, so if fewer of those people are uninsured, hospitals get reimbursed for more of the care they provide.

Yet there’s good reason to be skeptical about the boom times lasting.

In just a few years the government will cover only 90 percent of Medicaid costs—meaning states that expanded in response to Obamacare will have to figure out how to make up the difference.

Another problem is that as more people realize they’re eligible, they will start signing on as states have to pay more of the costs.

Finally, any true cost estimate is tricky because it assumes the federal government will keep its word about costly mandates. With Obamacare the situation is worse since cost projections have been sorely understated, and it’s still an open question whether the promised enrollment levels will be reached.