In my area, inoculations for children are $5-15 each at the clinics, and routine health problems for all are $100 or less (bronchitis, sprains, pneumonia, ear problems, etc.) The walk-in clinic that I use most often costs $80.
At the Children's Hospitals, for really serious problems, they treat first and ask for insurance or payment later. A lot of their costs are paid by charitable contributions.
If you want to have an MRI when you are in FL, maybe you should ask one of your Canadian doctors. It's sort of a joke here, but most Canadian doctors have earned their max salary in Canada by Sep or Oct. They then take jobs on cruise ships for free room and board. Canadian doctors who don't have children in school know quite a lot about FL health care.
I could be wrong with that anecdote about Canadian doctors, but the last 3 cruises I have taken have had Canadian doctors on board.