I don't know how much the chargers cost without subsidies. The greencarcongress article stated $4.2k installed after Japanese government subsidies.
Also, it's entirely possible the UK project ($4.3/W, $2.8/Wh) is far too expensive. EOS Energy, for example, claims $1/W and $0.16/Wh for their
Genesis zinc-air battery storage system. (initial price?) .. but this may not be full installation cost.
Decentralized EV storage definitely has a problem of power being unavailable when the grid needs it (either too few EVs are plugged in, or their charge is too low) .. and the standards are evolving rapidly enough that it's hard to say how long the chargers will be used. The LEAF V2H charger is a CHAdeMO plug. Will CHAdeMO be around in 10 years?
EV storage is more likely to be used for demand leveling than shifting between day/night generation/demand deltas. Smooth out wind / solar generation curves and absorb sudden spikes in demand.
This article has some links to historical stored energy costs; the UK project is high but not extraordinarily so.
http://bravenewclimate.com/2010/04/05/pumped-hydro-system-cost/