My first son spent a week in the NICU since he had to be on antibiotics, otherwise was fine. The hospital entered in my insurance card incorrectly so we were billed as uninsured. Turns out a week at the NICU for a healthy newborn is about $40,000!

It took almost 2 years of back and forth with my insurance provider and the hospital to clear up that bill. The hospital kept sending to to debt collectors too which was particularly annoying.

And to make it even more annoying, the hospital later changed it's policy on newborns on antibiotics - if they are otherwise healthy they don't need to stay in the NICU anymore. It would have saved us a lot of trouble.