We are looking at getting rid of our 2013 Honda Odyssey minivan with 103K miles on it and replacing is with a Toyota Prius, which my wife used to own before we got married, and loved, and would love to have again. She's fine with buying a used vehicle and I recently came across one on Carvana that I thought was ideal.
I found a 2011 Prius Four with just under 40K miles on it. It was listed for $14K which will likely be a little more than we will get for the minivan, but it will basically be a $5K or less outlay. It will take our avg gas mileage from about 25-28 to the upper 40s or lower 50s. Most cars this old have 100K miles on them, so this seemed like a good option.
But.... looking a bit on the all knowing internet I've seen thing like HV batteries only last 10 years and cost $5K to replace, so we have maybe 2 years until the $14K car suddenly costs us $19K. Also I saw comments about low mileage on a hybrid is bad for the battery and could cause even shorter battery life. On the same Priuschat forum I also saw people who said they were at 272K miles on their original HV battery, and some that replaced it at 151K etc. But will the low mileage and/or age cause a failure. How can I tell? Can I tell? Is it a crap shoot? Is this the reason people say hybrids are not all their cracked up to be? Is the hybrid a Mustachian (frugal, low cost) option, or is it just a consumer sucka in sheep's clothing?
That Prius uses a NiMH battery. This chemistry lasts the longest when kept in the 40% to 80% charge range, which is what the car does. batteries do self discharge, so the concern with low mile hybrids is that the battery has sat at a charge below 40%.
I don't know if there is a reliable test for determining the battery's health. I do there are ProLong chargers. These don't just charge the battery, but also rebalance the cells. What generally happens in an old battery is one cell's voltage drops out of sink with the rest. The way the pack is assembled means the bad cell can't be isolated, so the system cuts off an entire module. Bad batteries are usually just a case of some bad cells.
Which brings me to replacement cost. There are multiple small companies refurbishing 'bad' packs, and these cost far less than the $5000 you've seen; maybe even less than half. There could even be a nearby speciality shop that can repair your battery.
Then there are a lot of Prii on the roads. Most drove out their lives without needing a replacement battery.
With that year, the EGR system can become clogged with soot. Cleaning it out doesn't take much skill, but it is a messy job. The car can also develop oil eating abilities. Not an area I check, but the gen3 section of Priuschat will have a lot of info on maintenance and issues that this car might have.