In this case one could ask to see the price paid by insurance companies, not what is charged. Then offer to pay the same as they are paid by insurance, including a co-pay, of course. That way you would at least be on an equal footing with insured people. An office will be as cooperative as whomever is the receptionist, I suppose.
For a person with patience to search, the is medicare page is a start toward knowing typical coverage costs since many insurances track medicare rates now.
https://www.medicare.gov/coverage/surgery-estimating-costs.html
Keep in mind, however, for many tests there will be hidden costs such as the doctor who reads the scan. The whole process is endlessly complicated if you want to give up video games and twitter for a real life challenge!
