There's no comparison between what locals pay and what visitors pay, because the locals know their way around. In Rome, I took public transportation to Tivoli, visited Villa d'Este, went to Villa Adriana and back to Rome. Total transportation cost for one person: €6. I could have done the same by booking a tour in the hotel I stayed in for €59. That would have included two entry tickets (€14 together) and a guide.
What made the difference was a helpful man in the Rome tourist office, who explained for each leg of the trip which bus (the underground part was easy) to take in which direction, the name of the operator, and where to buy tickets. Even so, we must have bothered a dozen (very friendly) people or so with additional questions, got out at the wrong stop once, waited quite a bit at stops and had to walk at least as much to the monuments as within the monuments. If I would have valued my time at the price my clients pay, it would have been cheaper to take the tour.
Peter