I never knew hotel is included. That's great. Did you book directly from the Air China site? I am wondering if they do the same for other destinations, such as European cities.
Sorry that I overlooked your message earlier. The additional cost is $1000. Although I asked Air China for another destination, I thought my question was general enough that it should apply to other places as well. However, I'm not sure whether the cost is for both the outbound and inbound legs or just for one of them. I was only concerend with the outbound journey.