Interesting question, and complex societal issues too.
I nearly bought a new Nissan Leaf, but would need another car too for any round trips over about 100 miles: I calculated that I wouldn't use the Leaf enough to warrant the (a) high purchase price and (b) worse-than-average depreciation (your point about total cost of ownership being too high). Mind you, a two or three year old Leaf is only 10k.
But a plug-in electric car is just part of the 'spectrum' of alternative-fuel vehicles: my Honda Insight and Honda CR-Z are both electric-petrol hybrids - 7 and 8 years old respectively, with batteries that still work as good as new. They use regenerative braking and other clever technologies to save energy - so that they can have smaller and more economical petrol engines than a conventional petrol car of the same performance. Unlike a full electric, these two cars have held their value incredibly well and are currently barely depreciating at all. That's because...
- diesel car sales are down a lot
- petrol car sales are down a bit
- electrics are up a bit
-and petrol-electric hybrids are up a lot.
[Source: SMMT new registrations data]
People want to do something greener, but aren't necessarily ready for a plug-in electric with all its compromises, costs, shortcomings and uncertainties.
I've just ordered the brand-new CR-V hybrid as our family car. It's a proper electric car with it's own on-board generator driven by a petrol-powered Atkinson engine - the most efficient form of petrol engine at lowish speeds. The engine doesn't drive the car (although it can in some circumstances) - it just generates electricity with great efficiency. On my test drive, I did 62mpg around town without trying, which is not bad for a big SUV!
So, hybrids are coming on well, and are essentially the 'stop gap' to get us to full electric. One other point: people think electric cars have zero emissions, but that's only true if your nation's electricity infrastructure is 100 percent renewable! By moving the electricity generation away from the engine bay and into a power station, it's easy to overlook the real environmental impact of generating electricity. Also, as demand for grid-electricity increases, the price will increase too. That's just the reality of energy markets.