> Isn't that basically the same as me giving you $80?

In your accounting, you can claim that you have an investment worth $100 and book $100 worth of revenue. You're juicing your sales numbers to impress shareholders - presumably, without your $100, the investee wouldn't have bought $100 worth of your product. The last thing your shareholders want to see are your sales numbers stop growing, or heaven forbid, start shrinking.

Nvidia is not the first company to "buy" sales of its own product via simple or convoluted incentive schemes. The scheme will work for a while until it doesn't.