What is the less expansive way to go from Shanghai to Wuyuan?

Take a direct bus to WY from Shanghai South Bus Station. The bus departs at 18:05, and the fare is CNY 168. The trip takes about 6 hours.

The last bus departs at 16:20 from Licun Bus Station near Jingdezhen Railway Station. The trip takes about 2 hours, and the fare is about CNY 32.

To Sanqingshan, take a direct bus from WY Bus Station. The buses depart at 08:10, 11:00, 13:20, and 15:20. The trip takes about 1.5 hours.

Yes, the mountain is well worth a visit. You will be fascinated by its beautiful scenery. Have fun! :)

I'm only a girl travelling. It is safe at midnight to take a taxi for the hotel in WY?
Is enough to go to the mountain in one day, without sleeping?
What time is the last bus from the mountain to go back to WY?

Yes, it is safe for you to take a taxi to the hotel. The city is quite safe and sound.

Well, one day is too rush. You are advised to spare two or three days for the mountain.

The last bus departs at 18:50 from the eastern Jinsha Service of the mountain. :)