A couple thoughts.
1. The baby's NICU stay will be covered by Medicaid. That shouldn't cost them much OOP (this depends on the birthweight of the baby but I'm guessing the baby was less than 2lbs, 2oz). I'm guessing she was helicoptered off the cruise ship ($$$) and spent some time in a high risk maternity ward ($$$) so both those would be pricey but still not $1m.
2. As for traveling abroad at AMA - I asked, was told it was fine before 28 weeks. Landed back in the US at 23w 2d and got very lucky to not have been stuck abroad/had a micro-preemie in another country. I had a perfectly healthy pregnancy up until that point and I don't know if my doctors advice was due to AMA or just her general advice.
3. As for the baby being able to travel home by plane if discharged at 3 months old - it depends but I'd be surprised. The picture above shows the baby on a vent so it probably has lung issues. I asked about taking my son's pulmonologist about flying and they'd want to do a special test on him to test his oxygenation while creating an environment similar to air travel.
ETA: I think the $1m figure is a very common expectation hospitals put out there for babies born this early. It was the number we were told to expect for our son and he was born two weeks later than this baby. Our private insurance was billed $380k by the hospital (that's a four month stay at two different NICU and a surgery - I was shocked it was this low and have a bad feeling something else is lurking). Our OOP costs are $3k but we have yet to receive a bill for it.