Imaging while you are taking prednisone won't show the inflammation because it is "hidden" by prednisone.

The cost of doing an infusion might be less because the IV insertion and monitoring while you get the infusion are all a hospital expense. Hospital expenses should be covered by your insurance.

There is a concept of "bundling" hospital expenses. In some cases , the medications you receive while in the hospital are bundled up with the hospital expenses.

It just depends on your insurance policy. Insurance companies have a stake in this. I worked for an insurance company as a medical case manager for a brief period of time. I didn't like the job very much because the claim was frequently denied because the insurance contract didn't cover something. It was usually the employer that wanted to decrease their costs and buy the least expensive insurance policy.

Most of the work of a medical case manager involved negotiating with health care providers for an "all inclusive" rate as compared to everything being itemized. Maybe a person who works for your insurance company can provide better information. They might be able to negotiate something that decreases your costs. Doing this can be tricky because if the service isn't something that is covered by your insurance policy talking to someone might bring it to someone's attention.

Insurance claims department automatically flag some things for manual review but not most things. Most claims are paid without manual review because it is cheaper for the insurance company to just pay the claim without scrutinizing it too much.