Battery cost will depend on manufacture, size of battery and how many batteries your cart takes. 36volt carts take 6 batteries, the cost of these batteries from a leading deep cycle battery manufacturer will cost $900-$1000. 48volt carts take either (4) 12 volts or (6) 8 volts, the 4 x 12 volt battery cost is between $800-$900. The 6 x 8v will cost between $950-1050.
Keep in mind this price does not include any core charges. Most companies will charge $30 per core. Labor to replace batteries will range depending on the number of batteries, time and travel. As well as if the batteries are replaced on site or if you bring your cart into a shop.