If you used it on battery power for a year you could expect about half capacity in about 1 year. Cost varies but I think that depends on where you are in the world so my answer is go shopping.
Didn't anyone warn you to use AC whenever possible?
I received a message 7/1/13 from Toshiba that my battery life is relatively poor. I looked at the Toshiba PC Health Monitor and everything looks fine but the battery. I purchased this laptop Feb.2012. Why would my battery life be poor and how much does that cost if worth the replacement?
I use this laptop everyday for work.
Toshiba P755 core i7 2670qm cpu @2.20ghz