Transportation cost from airport to hotel and hotel to terracotta army museum

Of couse bus is much cheaper. You can take shuttle bus line Nan Shao Men Xian Hotel Line to Xian Hotel and then walk about 100m to take bus line 603 to Bell Tower. Walk about 100m you can get the hotel. The fare is about CNY 30. If you take a taxi, it costs about CNY 100.
The best way to Terracotto Army is to walk about 100m and take bus line 16/ K16 to Railway Station East then transfer to bus line 914 to Terracotto Army. The fare is about CNY 15.