My friend who recently had a one-day private tour in Xi'an paid 1200 RMB for a car, driver, English-speaking guide, airport transfers, and admission to the Terracotta Warriors, Big Goose Pagoda, and the famous hot springs (that I can't remember the name of). Lunch may have been included, too -- I don't recall. This amount included an understanding that she would not be taken to shops or restaurants where guides get kickbacks, i.e., that she would spend her time at the sites.