They eventually give up when they realize you're not going to give them anything.
Happened to my parents and me when they picked me up from my mission in Mexico City.
I just kept telling them they weren't getting even 1 peso. They started at like $1000, and slowly got down to like $10. I finally got pissed off and pretended to call the us embassy to report him. They finally gave my dad's license back and we drove off.