If we assume an ambulance+equipment costs $500k and has to be replaced every 5 years, requires 4 personnel around the clock to operate with the cost of employing one being $50/h, one ambulance getting an average of 4 calls per day and per call average costs of gas, medicine and other disposable stuff being $300 we are looking at about per ride cost of $1500 so if one ambulance ride costs 12k as per the other comment, we are looking at a profit margin of 87.5% even with these very likely way too high cost estimations.