[throwaway_ghj]

People become entitled like that, basically because you let them by repeatedly allowing them to take your time for free.

Compare with: "Sure, I'd love to do that. I can spend about 10 hours on that this week and that will cost you $1000. Who do I address the invoice to?"

That should sort the wheat from the chaff pretty quickly.

[will_pseudonym]

Yup! This is also applicable for people who won't pay you back with their time, either! What helps some people is to have plenty of stuff going on in your life so that it's easier to say no because there actually are a ton of compelling things you want to spend your time on...