ATV batteries cost anywhere between $30 to $100, depending on the model and retailer. Amazon.com sells a YTX9-BS ATV battery for $30, as of 2016. It is a 12V 8AH battery with 135 Cold Cranking Amps. It is also rechargeable and has a high discharge rate.
Amazon.com also has a $100 YTX9-BS 9BS Lithium Ion battery with 12 volts and 300 Cold Cranking Amps. This version features a lower volume and weight, requires no maintenance for a year and is better for the environment. The life cycle reaches 2,000 cycles, which is significantly longer than the typical 150-300 cycles for other batteries.