The line items look like a pretty standard "workup", as they call it. The blood and urine tests are probably a fishing expedition to make sure you don't have some other bizarre disease. If it turns out you did have this hypothetical bizarre disease, I'm sure you'd be disappointed if the emergency department missed it.

$7k CT seems pretty steep, but CTs are also a marvel of modern technology. I know MRIs have a price floor because they need medical grade liquid helium for cooling, which is thousands per liter. I don't know if CT has a similar consumable item or not.

I would hazard a guess that most real kidney stones would be revealed by x ray. But it's also possible that x ray would not reveal other physiological abnormalities that could be causing your symptoms.