The battery itself costs around $100.00 and if you have a shop change out the battery it might cost you $50.00 in labor to change the battery.
Most places that you buy a battery from will replace the car battery for free if you buy the battery from them.
A battery is not too hard to replace yourself if you're able and can connect a positive "red cable" to the + side of the battery and a negative "black cable" to the - side of the battery.