Qingcheng Moutain is quite far away from CTU. By-metre taxi service is not possible for such a long distance, especially at night. But IMHO, 500 RMB would be quite enough for this trip.

I once took a taxi with three other guys at 3:00 am from Chengdu to my home town, which is almost the same distance of that from CTU to Qingcheng shan. It cost 300RMB for us four.