Pretty sure he's not getting beat up by any pimps when he strolls into work each day, either.
He worked really hard, too. I mean, I wasn't paying the bills, but he definitely seemed worth the cash. Filed some awesome stuff for us -- you don't often read legalese that entertaining.
You probably took that into consideration with your response - I'm not disagreeing with you, just making it clearer.
And yes, there are many jobs where the pay rate exceeds $300 / hour. In my field (business coaching - no formal qualifications necessary, though they may help) a Harvard Business Review study found the average charge-out rate is $500/hr, the top measure is $2400/hr, and most practitioners work solo so don't split that fee with anyone else.
But the difference is that the lawyer was probably working 50-60 billable hours a week, whereas an escort (or a business coach, presumably) will work significantly less than that.
The worst you get from ordinary supply curves is diminishing returns. If you paid $1,000,000 per bushel of apples, well, you're just throwing away money--I'm sure we'd max out the earth's apple-growing capacity well before $500,000 per bushel. Labor's the only supply curve that actually bends back.