Thanks a lot for the info. Couldn't find it on the net.
I just came back from Dapu. There is only one bus to Xiamen daily, the one at 6.40am. They have discontinued the 12.50pm trip. Since 6.40am is too early, I decided to cut short my Dapu visit and left one day earlier. I extended my car rental for another day so that the driver can send me back to Xiamen, instead of using the public bus.
I don't know the fare because I did not take the bus. The car rental is rmb400 a day. Might be more now. You can read more about my trip at my blog http://casey53.blogspot.com