The medicare/medicaid funding for hospitals is very low (especially considering the cost for service). It's normally highly subsidized by what they bill private insurance/private pay. Having an ER is often a loss depending on the demographics of the area (% of insured folks).
For an ambulance service, it's not too bad though since it's pretty set in stone for the year and can be planned/budgeted (just a pain to figure out due to the adjustments/coinsurance rules - what you bill vs. what they allow vs. what they actually pay). The medicare reimbursement rates are public information. For many services however, there is a different rate for facilities which have a contract, if you're in a competitive environment, it's going to be close to the medicare amount - if the service is acting legally. Every service ends up subsidizing a little bit with revenue generated by private insurance patients as medicare reimbursement tends to be right at the cusp of covering costs for all but the bigger agencies.
