I was tempted to title this: "SB's do not think." :p
Anyway, your understanding that $1k in sugar could equal 2 - 3 pro bookings is spot on. However, no SB, or at least no true civilian SB is thinking about hooker rates in her area. In addition, SB's don't consider their asks for sugar from a competitive point of view. They see this as a very personal issue: "How much do --- I --- want to sleep with some old guy?" and not "How much will this guy pay for sex?"
Trying to make her see the competitive landscape in your attempt to negotiate will almost always lead to the argument of her "worth." Once you get to that "Hey, Mr TtCttc2, I am WORTH at least $1k!" position you are lost. You will never be able to convince her she is not worth whatever she asks. Every woman's "worth" is "priceless." Just ask her. :p
Instead, you can counter the outrageous asks by sticking with YOUR budget. "Wow, I'd love to give you that much help. Unfortunately, my buget is closer to $300 per date. Do you think we can make that work?" You sidestep (actually you passively validate!) her worth and center the negotiation around your budget. She may come back with a better offer. Or she do you a favor and bail, saving you time to move on.
Finally, to answer your last question: Yes, someone is paying these stupid-high rates - sadly. But that should not change your negotiating tactics.
Life is good
The Cat