How long do you suppose it's going to take to make back their investment? For it to pay off in ten years they'd have to be making fifty dollars a month from arbitrage.
FWIW, Ford has sold out of these for the next 2 years, so they must be doing something right.
But honestly I don't know, it's not something I've looked into. If prices become increasingly variable coupled to demand and impact of generation source at time of use, I imagine it could be quite lucrative and that might be a useful incentive to get effectively decentralized peaker plants in the form of grid-tied residential batteries caching cheap cleanly-sourced electricity.
$32 / MWh wholesale is an arbitrage that could be done on many days in CAISO today. I don't particularly think that people will use that much of their battery or do so every day of course but it does show that it's not an orders of magnitude implausible scenario either.
So I can do the electricity math for myself, but not for others.