How much should staffing agencies get above my hourly billable rate?

 In NYC, Morgan Stanley implemented a policy where the staffing agency
could not make more than 20.00/hour off the consultant. E.g., if I get
47/hour, the total billable hourly is 67.

I wish there were some way to know how much the agency is getting
hourly on my behalf.

What is a fair amount to charge above the consultants hourly rate on
1099 or W-2?

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