As a promoter I can tell you every single area is different. I have paid as little as $100 to have an ambulance at a facility, but I have also paid as much as $1000. One other thing that has changed over the last 5 years is the transport rules. At just about every single venue we work with, if the Hospital is more than 5min. away, they will call for a 2nd unit to transport. Also in several areas, fire departments are the main ambulance service. Now you have EMT's and not Paramedics working your events. This is also a big factor in price. I have read several comments here from people who have no clue what they are talking about. An ambulance on site means nothing if it is not able to transport. So many more things I can add to this, but many would not believe me.