A medium one nationwide for any criminal background, credit check and other basic information is about $300. Or rather was about $300 but that was a few years ago. Just a credit check used to be around fifty.
If you want worldwide at least $500 and it will be spotty.
If you are checking out a potential employee go with the nationwide criminal. If it is a potential spouse for you or relative go to a real detective agency. It will be about a thousand but this is one time you do not want to be cheap.
However, a TS/SCI background check is clear and costly IF you are asking for security clearance, in that case, cost may range up to 60k.