It's a stupid game because it's really really rare for this kind of arbitrage to exist in the system, especially if you do the computation correctly and count after-tax income rather than pre-tax income.

In the rare instances where you profit, congratulations, I guess? I haven't ever heard of a single person who got rich off of car loan arbitrage. None. But I know tons of people who got rich off of never borrowing a car loan. A $700 per month payment stream invested at 5% over 30 years is half a million dollars. I'd rather have $500000 than a permanent car loan.