I want to travel from Xiamen City, Fujian Province to Tai'an City, Shandong Province. How much is the average airfare?

There is no direct trains or flights to reach your destination city from Xiamen, so it is suggested to fly to reach Jinan and then change to take a bus to reach TA.
For the flight tickets, I am afraid that it is hard to tell. It is very easy to get a large discount if you buy in advance. It is suggested to look at the official website of the airline companies. Shandong and Xiamen Airlines operate that routes.