I tried Google and ended up with this official Boeing price list:

http://www.boeing.com/commercial/prices/

As has already been mentioned, airlines never pay the full price because (sizable) discounts are always given. This is merely a starting point. Often savings are given that are indirect. Boeing for instance paying for crew training, support costs, maintenance costs etc.

Anyway, according to the list a B737-700 goes for 47 to 55 million USDollar. The price depending on the amount of toys you install on it. Obviously a plane with IFE or winglets will cost more than a plane without.