I have demonstrated my ability to convince clients to pay amounts of money like this for my skills. And yes, the not-so-secret thing about consulting is that if you're able to convince a client that you're worth $500 an hour, it's just easy to convince them to pay $300 an hour for the work of a colleague of yours they've never seen.
Ugh, I encountered this a few times early in my career (early 2000s.) The worst case was a team from a large, expensive, high-end consulting company. There was one A player who was fast and sharp and absolutely invaluable, two developers who were slow but diligent, one guy who everybody avoided because he was pissed off that he wasn't as smart as the A player, and one engineer who spent all day in front of an IDE but never checked in any code. Once, as a prank, a couple of my coworkers sent me over to "help" this last person (to be clear, the prank was on both me and the person I was sent to help.) They were staring at code that was just syntactically wrong, and not in a subtle way. It was a Java source file, and the line that they were working on, which I think was the only line they had changed, did not look like Java. They couldn't see what was wrong with it, and honestly neither could I, in the sense that I could only see that it didn't look like Java. This person had been "working" on the project for several weeks, and from that point on, I felt intensely sorry them, because they came to work every day for eight hours, and sat in a chair looking at an IDE, going to meetings, staying late if the A player stayed late, etc., nobody ever talking to them, and I can't imagine what kind of bizarre hell that was for them. I didn't feel comfortable talking to them about it because there was an age and culture and language gap, so I'll never know. When the consulting' contract was up, we renewed, but that person was replaced with another slow but diligent worker, and I never saw them again.