I've owned my Chevy Volt for 4 years now. In that time I have saved an average of about $100 per month in gasoline (net - after accounting for charging costs) . That means I've saved approximately $4800 so far in gasoline costs. I've also only needed one oil change so far since I rarely use the ICE. So say another $200 in savings there. Also, my brakes are good as new still thanks to regenerative braking.
My Volt cost me about $25k after my $7500 tax credit (which I make enough income to have fully realized).
Minus $5k in gas and oil savings so far means a net cost of about $20k at this point. Any car which is even close to it in terms of performance, safety and quality of the ride, etc. would have cost me significantly more. Even without the tax credit - I'd be at parity now. Yes, eventually in another 10 years or so, I may want to replace the battery pack. That will be a significant cost. But in the meantime, the savings in gas, oil, brake servicing, transmission and engine servicing will more than have paid for that cost.
We recently bought a Chrysler Pacifica PHEV for my wife. The savings are already accumulating for it as well.
The cost of ownership of EVs and PHEVs (if driven mostly in electric mode) is so much lower compared to ICEs that even without federal tax credits, etc, there are several models which now are low enough cost to mean that over their lifespan they are likely to save the owners money.
BUT - in the end - it's not only about money. If the were the case, we'd all be driving the cheapest tin can on wheels. We all choose to strike a balance between cost and features when choosing a vehicle. Even ignoring the environmental benefits - the amazing torque, quiet ride and wonderful convenience of not having to fill up my gas tank once or twice a week, are features I'd be willing to pay extra for. It's just a bonus that it turns out I don't have to.
I will never purchase a gas only vehicle again. I do own an 2001 Toyota Tundra pick up truck I use for hauling, towing, etc. Once there's a suitable EV or PHEV replacement available, I will be replacing it as well.