There are three types of taxis in Beijing, and the most common type, the type with the number "1.80" in a circle on the window, will cost about Y100+Y10 toll (or less) to get to most anywhere in Beijing from the airport. To get one of these taxis, the key (as always in China) is to avoid ALL the touts inside the airport and go outside to the very obvious taxi queue. You will also need your hotel name written in Chinese characters. Even better would be that plus an indication on a map.

However, the Y250 charge is less outrageous than many other hotels charge (the Grand Hyatt, for example, charges Y750 for this service) and if this is your first time in China, you may want to use this service for peace of mind -- you will be met by someone holding a placard with the name of the hotel, even if your flight is very late.