Per Chart Coding Rate

Why is there such a variation in coding per chart rates? You look on the internet forums and there is a HUGE discrepancy and it is very confusing.

Remote coding companies generally have to be competitive so what is the standard going rate for a remote coding company? But an individual consultant can charge so much more. Why such a variation??? And finally, do companies have two separate fees: One for per chart and then one for a more focused audit? If so what are good competitive fees for that?

Can anyone provide me with a rate sheet that is pretty standard in the industry? I would like to know going rates for E&M, surgery and oncology please.

Thank you in advance!!!!