I guess it depends on the quantity of the order, too. And note that no one actually pays the list price provided on Boeing website.
BTW, if you're freaked out that 744 is cheaper than 773, you should read some sources that say A380 launch prices were below that of 747. Imagine A380 being cheaper than 773.
Although the 773 is listed higher than the 744, lots of bargaining and price cuts go on between boeing and airlines when negotionating the purchasing of these different aircrafts. When all said and done, very easily you may see a 773 actually cost less than a 744 considering the fact that the 773's not really been selling to well.