Sometimes you pay extra for stuff you may not have needed; but the facility has on hand. I've seen vet facilities that rival human ERs for high-tech stuff.
On the other hand, my own vet has a modest place in the middle of nowhere. And today, my Cattle Dog was going crazy itching/pacing/panting - so they squeezed me in between appointments, checked him over real well, gave me prednisone to stop the apparent allergic reaction PLUS did a needle biopsy on a strange lump that turned out to be a large cyst - and the bill came to $55. I sure wish I could find a medical doctor who treats ME as well as my Vet treats my dogs :-)