The dealership replacement of a Prius battery with parts and labor was about $8k (circa last summer). I knwo several people that bought a Prius. One guy had a manufacturing defect and the battery had to be replaced. He said it was $8k but covered under warranty to get it fixed. He also said that he is not getting near the mileage he expected. That is probably due to his driving style. Lots of long highway miles with a canoe strapped to the top.
This may have now come down like the halogen headlight bulbs of the late 80's and early 90's. The dealers charged $28 for them and a year later they were $9. I haven't bought one in a long time but I imagine they are lower.
I have a Prius and lurk on several online Prius forums. Folks with accident damage seem to be quoted $1-2k to replace the battery pack nowadays. The prices are definitely coming down, both as a result of volume increase and because battery packs from old or junked Priii are starting to fill the pipeline for recycling.
What galls me about threads like this is the eagerness of folks to believe things they earnestly want to believe. It’s the exact point-and-laugh mentality seen in Bush Derangement Syndrome, just directed in a different vector. Folks, don’t believe everything you read. Investigate a little. Better yet, in this case maybe talk to an owner, and you’ll find that this is a fantastic, capacious, safe, fast, reliable and durable car that just happens to put fewer dollars into the pockets of sheikhs and jihadis.