varies wildly from place to place and weekend to weekday.
Least I have paid from the majors in North America for an econo/compact car was around $15 USD and the most in Mexico or Europe/Australia for intermediate was around $55 USD. Typically I pay $20 USD for weekends and $30-40 USD for weekdays in North America.
My best rates come from discount codes, e.g. elite frequent flyer program discount.