Depends on aspect. Its actually not cheap to run an ambulence with the required personel and materials swapped often on call. I believe the main reason why its expemsive is because more often then not, the ambulence isnt paid for so said company takes a loss.

ambulence costs are also tied down by law in some cities, so for those specific cities, its the city making the cost, not the company.

For Europe, the bulk of the cost is covered by theor health care, so their out of pocket cost is low. In the U.S, its broken because insurance often denies the ride depending on insurance company and documentation.