It depends on various factors. It could be demand and supply of available types of rooms, room size, window views or not, amenities. At times, the hotel wants to sell more standard king and costs it cheaper.
The hotel is right outside of the metro if you come out of the correct exit. I can't remember the exit but it might have been H. You can take an escalator up, you will see a few small restaurants and then go up a few more stairs to the outside and if you look to your left the hotel is right there, you can't miss it.
Take the metro to the pandas and go early! I was there by 8am but wouldn't arrive much later because the crowds grow quickly. Take the metro to Panda Ave, exit the metro station by following the signs for the Panda Research Base. Outside of the metro is a small building and you can buy your admission ticket and shuttle ticket to the base. The shuttle will take you directly there. You will need to buy a second ticket for the shuttle if you decide to return the same way. The whole thing takes about an hour...maybe a little more depending on the day and time. 45+/- minutes on the metro, 10+/- minutes on the shuttle. Have fun!