So it's additional supply of both material and embedded energy that otherwise could go to someone else, or wouldn't need to be spent until you were sending you old car off to be salvaged.

There's a time value to it as well, just like with amortized financials.

Think of it this way: if everyone used that strategy, we'd have twice as big of a vehicle market, requiring twice as much material and energy.

Even if you expect each vehicle to last twice as long, it all has to be paid for with capital costs up front. Both your cash out of pocket, as well as manufacturing capacity and energy/resource extraction.

You might get effective use efficiency of 50% for twice as long, but the overall cost in dollars, energy, and emissions is much greater because of amortization.