Yep, at some point the math is very blatantly obvious. So obvious that you just cannot help it .... it's like we could create a simple chart with few questions to answer and few number to plug-in ... the result would be, yes you should be in the market for an EV of some sort or no you are not t this point yet. Whether pure EV or very capable form of EV like Volt, that depends on individual circumstances.
You don't mention what they drive now, but I guess, it's either old in need of replacement or expensive fix, or it's thirsty. The only other thing I'd say is, that they do realize they can have the Volt now (whether new or used), but they will have to wait for the Bolt until Mar or somewhere there?
With the car I am trading in, it's fuel consumption, type of gas ... at current electricity rates, the Soul will cost me 1/10 of fuel money ... and that assumes I will only charge at home (which will not be the case), at off-peak rate and will consume 20kWh/100km of juice, which I don't think will be nearly as bad when yearly average is worked out. That is a nice song to listen to .... LOL