Obviously, you never have owned a business. But I don't quite follow your thought train.You're not being honest if you pretend your hourly rate is $50 but your clients are actually paying $300/hr.
You come to my shop for an engine overhaul. I give you a written estimate with a $50/hr labor rate and an itemized A-Z list of other charges. Complete turn-key. At the bottom is the total cost. You accept it or not. As you said it's not the clients job to figure out my rates or costs. So where is the fraud or money laundering?
How would you charge for such a job? I'm always open to new ideas.