My Assumption on this car is that more than 50% of the mileage will be on the gas engine (thats allot of miles for a 2013 like mine, the previous owner had a crazy long commute). I also feel like volts should go longer than some other vehicles because the battery tech is solid, and the engine will have less mileage than other cars with 100k plus miles on them, transmission does not wear like other cars (still learning but the fluid was sure clean with no records of it ever being changed!). Plus most vehicles these days should go over 150k.
Is this a premium volt? If not you can probably find one private party for less with that many miles on it. 8.4k out the door isn't bad though, I had to pay nearly $800 in taxes when I got mine for 8k.
Any used car out of warranty has potential for costly repairs. A volt with less than 60k miles on it is going to be significantly more expensive, and I think only the battery, and maybe catalytic converters will be under warranty.
The difference on the volt is that some require special tools / a trip to the dealer to fix them. It's all a trade off. After doing the maintenance I was amazed how little maintenance this car actually requires. I would make sure the dealer has changed the spark plugs and transmission fluid. Maybe see if they will do a coolant and brake flush / air filter as part of buying the car. Then your good to go for a long time
100,000 mile/8-year Lithium-ion Battery Pack Warranty (this one is nice mine is covered for 150k so almost there but not there yet)
100,000 mile/5-year transferable Engine Limited Warranty (for Range Extender) (I am not as worried about this one)
5 yr/60,000 mi powertrain (this one is important but still, volt under 60k / 5 years old is going to be allot more expensive)
100,000 mile/5-year 24/7 Roadside Assistance Program (dont care)
100,000 mile/5-year 24/7 Courtesy Transportation Program (dont care)
36,000 mile/ 3-year no deductible Bumper-to-Bumper transferable warranty (don't expect to get this on used cars, or have it last long if you do)
100,000 mile/6-year corrosion protection (no big deal for me but might be a bigger deal for salt states, but you can inspect the car for this anyways)
So really what are you worried about breaking? Most things that would be covered under warranty are not going to be under warranty very long anyways. The exception being the battery (and generator I guess), but if your worried about the battery, why buy an EV?