Depends on the model. Prius batteries generally last 8-12 years (with a few going 15+) and the Ni-MH batteries cost ~$1,500 for reconditioned used, ~$2,000 for new Chinese, and ~$4,000 for new OE. Mine lasted 9 years & 160,000 and I opted for the $2,000 chinese battery with a 4 year warranty. Install was free. The mid 2000s highlander hybrid battery costs a few hundred more. Mid 2000s Civic costs a couple hundred less.
Mine was on the shorter end of the life because I do a fair bit of mountain driving which rapidly depletes and recharges the battery, accelerating wear. Long downgrades also "overcharge" the battery - that is, charge it to 100% rather than the normal 80% which is best for battery life. On the other hand, I didn't need to replace the front brake pads until 150,000 miles and I'm still on the original rear brakes.
The lithium-ion batteries are too new, but should last longer (and be more expensive to replace).