Maryland would have to face the real cost of providing universal healthcare
The point is that they would have to face much more than the real costs of providing universal health care because they would have to provide care to a lot of people that never paid into the system due to migration.
There's a good suggestion for dealing with this above: https://news.ycombinator.com/item?id=14556688
On "unbridled state to state migration", I already covered that. Maryland would have to face the real cost of providing universal healthcare, and residents would have to decide whether it's still worth it to live there. Many sick people would decide that it's not, and choose to stay put in Virginia.
And if it truly wouldn't work, then it begs the question: Does it really work on the federal level? Why are costs skyrocketing and providers leaving exchanges?