If one has a Prius that's out
If one has a Prius that's out of warranty, he or she may still be able to qualify for a "Goodwill" discount from Toyota of America. Discuss it with the dealer and call Toyota's offices. If one ends up buying a battery pack, Toyota's replacement beats Dorman's by a fair bit. The battery from Toyota costs more, but uses new cells, Dormans are old cells with the bad ones replaced--with old cells. The cost comparison is Dorman about $1500 with a three year warranty versus Toyota (less than $2000 if one shops the internet, the Toyota battery also has a 3 year warranty if you have a dealer do the install,
but the new cells should be expected to last the lifetime of the car.
I have a couple of Gen 1 Prii, and I really like them!