That is the car dealership acting as a bank, and managing your savings for you.
No, in such a system the dealer would need to forward the value himself ASAP. The value would be in perpetual motion and no party would manage it for a length of time.
He is "managing" that savings by moving it along so that it does not lose value. Yet, he still keeps track of how much you have paid in, and when the payments equal the value of the car, you get the saved value, which he has been holding for you, in the form of a car.
see:
https://en.wikipedia.org/wiki/LayawayTry again. How can I make a large purchase without saving or going into debt?
Barter? Which implies "saving" in a way that has already enabled progress of value, like mentioned previously.
I don't see another logical way.
Simple. You don't. You can
not make a large purchase without either saving, or going into debt.
You consistently confuse consumption with investment and in a most biased way. For you every time something is 'saved' its an investment, and every time something is 'consumed' it's a wasteful act of gluttony and immediate gratification.
I make no such value judgments. In fact, quite the opposite:
Consumption is a vital economic activity. Not just eating, but cars, household goods, anything that either loses value over time, or is consumed by use. People need these things, and you can't just eliminate it, or even really discourage it very much without hurting the economy.
At least read the things you quote.
EDIT: You may want to check your math, 100-7 is 93, not -92. (and who the hell charges interest on trees, anyhow?)