You might. I can't speak for Volts but 60 seconds of Google confirmed what I found previously about Priuses: $800-$1500, in your driveway. You can also replace individual cells. Those batteries (I'm amused that Toyota now calls it the "traction battery") last a long time. When we traded in our 2005 Prius recently it had 165,000 miles on it and would still get 50mpg on a good day. The battery was fine but repairing the air conditioning would have cost more than the car was worth.