My uncle told me to charge $15 an hour for my first logo design. I did it and the client asked for 12 revisions. | First Gig Pricing - Freelance Forum - The Community for Independent Professionals
I used to think charging for extra revisions was just nickel-and-diming people, but after a few nightmare projects that went on for WEEKS past schedule, I totally get it now. Three rounds is actually generous if you think about it, and adding a fee for more keeps things moving instead of letting clients tweak forever. Your sanity being part of the price tag actually makes total sense to me now.
Consider putting a clear limit on revisions right in your first message to a client. I learned to say the price covers three rounds of changes, and any more cost extra per round. It sets a boundary early and stops the endless tweaks.