The problem is here:

> Let's say I give you $100 on the condition that you buy $100 worth of product from me. And let's say that product cost me $80 to produce. Isn't that basically the same as me giving you $80?

Why limit myself to $100 for a product that costs $80? I could just as well give you $1 000 000 to buy this same product from me. That way, I have a $1 000 000 share of your company, and I have $1 000 000 in revenue, and it only cost me $80.

This distorts the market for the product we're trading, and distorts the share price for both my company and yours.