How much does it cost to add a half bathroom to your house?

I added a bathroom to my home, and it cost $7,400 (not including the sink,toilet or anything) but that was the price of the foundation,roof,beams, siding, pipes, and septic hook up. (this is the price for a full bath size also) == Figure on a minimum of $250 per square foot if the space for it does not exist, $150 if the space exists, but has yet to be finished.