You do know that the Model S right now, is the cheapest car in it's class right ?
Or do you think "floor price" is the only price that comes into calculating the price of a car. Nearly all cars have higher maintenance costs over their lifetime than the floor-price, the second-hand price is a huge factor (the more value lost, the worst it works out when you want to upgrade) and of course the fuel cost.
Factor all those in and the model S is cheaper than any other car in the luxury sedan class - and offers out-of-the-box far more features than any you can get for the same price.
The best second hand car to buy in my country, South Africa, right now is the BMW 3xx Diesel. This is because
1) Those cars have a very long life
2) Being built locally - they are adjusted to the quality of our roads - excellent cars like Renaults or Chevolet's just don't LAST here.
3) A second-hand BMW 3-series, now about 10 years old, can be resold in 5 years for about 90% of what you pay for it ( which is not much).
4) It has absolutely top of the range luxury and safety features.
In fact, buying that 10 year old BMW works out MUCH cheaper than buying a brand-new car for R10K more, because the car you can GET for R10K more is going to be something like a fiat palio or or other bottom-of-the-range car that will lose far more value as you drive it off the lot, cost you a LOT more in maintenance and uses a much more expensive fuel - and it will be a much less safe car to drive.
My 8 year old Audi A3 is pretty much the second best choice right now after the BMW, but when I upgrade in the near future (now that I have a kid, a four-door becomes valuable) I will probably look at BMW.
There is SO much more to calculating the price of a car than the number written on the windscreen at the dealer - and when you actually DO those sums - there is NO car that's comparable to the model-S in features (or anywhere close) that isn't FAR more expensive a vehicle to own.
In the meantime battery costs will keep plummeting - just the scale-up in production alone will ensure that, throw in improved engineering in the batteries themselves and you're set for a few years of huge drops. Since the battery right now is the most expensive part of the Model-S - don't be surprized if even the sticker price drops dramatically over the next few years.
Frankly if I am ever stupid enough to buy a NEW car in my life, I won't consider doing that with anything EXCEPT a Tesla, it's literally the ONLY car that offers anything that even VAGUELY resembles value for money if you buy it new.