Sadly there are alot of hospitals who will screw people over by overcharging for little things here and there. I read an article about it. Overzealous/shady hospital administrators charge for the most ridiculous things that you didn't even get. Happened to my mom. You should always check over a hospital bill.
Not only overcharging but a simple keying error on a billing form can turn a $200 blood test into a $22,000 procedure, all because someone transposed a number.
It's also important to make sure your insurance pays their portion on time and at the amount they are contracted to pay.