The mere fact that you have batteries being swapped in and out of cars means you can systematically track battery health and refurbish batteries that are getting low, without ever having to bother the customer or affect the driveability of the car.
The $40 (or so) battery swap fee is not for the electricity or the infrastructure, it is an insurance payment on the battery itself. You're paying for the collective maintenance of all Tesla batteries, and in turn ensuring the health and ease of your own.
The last remaining argument against electric has always been the charge time, and "oh, but the battery costs $15,000 when it finally dies out"—I always knew a system of battery swap was the answer to basically everything, and I thought Tesla was doing it wrong by coming out with a fixed-battery car.
Turns out I was wrong. They're doing everything exactly right.
A battery pack swap will cost between $60 and $80,
about the same as filling up a 15-gallon gas tank,
Musk said. Drivers who choose to swap must reclaim
their original battery on their return trip or pay
the difference in cost for the new pack.
I hope that's where they're going, because it's the crux of the concept to me.
Otherwise you're charging it at home, at work, or using a supercharger while you eat lunch.
You may only swap the batt 10 times or less in those 37,500 miles. And you still get all the battery-quality advantages.
If you were to swap the battery every time, this would look to be a poor bargain. But if the battery is swapped only once per ten "empties", because for the other 9 it was convenient to charge it, then the calculation would be redone for 10x the distance at the same price.
So, you are both right, but talking about slightly different things (typical use for a commuter with occasional trips, vs long-distance-only users).
Now you also have the choice of swapping, which provides you with a guarantee of a constantly healthy battery, a fast full charge, and continuous long-distance capability.
I see your point—if you're doing 37,500 miles of long-distance, you're going to eventually pay for the battery cost over time. Possibly. But you have the choice, and it's going to be amortized over so many snap decisions that it's more like, "the convenience of this is worth $40 to me right now," rather than thinking of it as the cost of a new battery.
I think it works out, personally. And for most people, charging is a perfectly acceptable way to drive the car. I think people won't really swap the battery that often, and when they do it'll be because they need the time benefit, and that's the value proposition.
For others, they get the same battery-life and battery-health benefits by swapping only once in a while, or hell, even only when their current battery dies completely. Basically, everyone wins, and it's still about the same cost as gas for a 22mpg car, even if you swap 50% of the time. If you swap less than that, it's cheaper to operate in the same period of time. Simple as that.
So that makes about 7 years (pessimistic) to pay as much as for a new battery pack.
So, use a bigger number than 100, it helps some, but not tremendously.