We just returned from a trip to Florence where we were listening to the Rick Steves Florence - A Renaissance Walk. Turns out there is a gelateria that is scamming people based on this audio guide. Right around the time where the tour is talking about gelato you arrive at this non descript place. It looks family run. If you accidentally step in you will get scammed with 10-15 Euro servings, cash only and the crappiest gelato you could ever have.
The address of the place is Via dei Calzaiuoli 79R. It goes by different names (Gelateria, Gelateria Vegana, Vlad)
Check out the Yelp and TripAdvisor reviews for more details. Would highly recommend a warning about this place.