A Microsoft director who ran a portfolio of product teams reached out to ask about a "collaboration". I said I'd be happy to send them my consulting agreement. There was a little grumbling about the rate but I just reiterated that it was my rate. After a lot of legal back and forth, they signed, I answered a bunch of questions for them in a 2-day workshop, and they paid.
If they want you badly enough, they'll pay. Don't work for free.