[RedDevil]

This has been discussed before quite often, you can get more than you want to know by searching this site.
Not to be pedantic, we just want to avoid repeating ourselves over and over again.

In a nutshell, yes battery replacement is quite costly - though it varies per make.
The life expectancy is mainly reduced by heat. Park your EV in the shade on hot days.
Next comes running it down to zero or overcharging it. Most battery types degrade slowest when used around the 50% state of charge.
Time also kills batteries, don't expect your Lithium Ion pack to last more than 10 years even if well kept (though that helps).
And of course usage does eventually reduce the battery capacity.

The plus side it that most EVs need very little maintenance; the brakes get hardly used, there is no cooling system, intake filter, exhaust (cats!), oil, spark plugs, clutch, gearbox etc. to tend or replace. Just fill the window washer liquid and go.

The minus is battery life, tire wear (EV's are usually slightly heavier than comparable gas cars), short range and long charging time.

It is really hard to give a 1 on 1 comparison of EV's and gas cars consumption wise. As an EV will do start-stop city traffic in mild weather very efficiently, and highway runs in winter less so. In a gas car the heater operates more or less free, in an EV it eats into the power and thus range.

That said, you can do about 100 miles with a Leaf; you'd do 4 to 5 miles for every kWh used. In a comparable gas car (I had a Nissan Almera which was more or less the same size) you'd do 9 miles per liter (35 mpg). I did, when I really tried hard enough.
Somy rough estimate would be 2 kWh for every liter used.
Then you'd lose some in charger losses etc. so say 2.5 kWh.
Over here that is still just 1/3 of the cost of a liter of gas.

And there you have it. The fuel cost of an EV is so much lower than a gas car that that alone more or less makes up for the battery replacement cost, if it ever comes to that.
The gain comes from not having to do all the maintenance and replacements a gas car needs.

Bin the calculator now. The EV has another plus; it is more fun to drive.
It is almost silent and very smooth. It gives you much more control with much less effort than a gas car would. Acceleration is instantaneous; you really feel the right pedal controls the power, directly and well measured.
You really need to do a test drive to appreciate this fully. It is much like driving a CVT hybrid, but without the noise and more powerful.

So, yes an EV is an economical alternative. And a fun one. And probably an impractical one, but that depends on your needs.