What he means is simple. Like at least 1 other poster, you seem to have considered the numbers I gave to represent capital investment: invest $100k, make $20k vs. invest $1M, make $50k.

But that's not the scenario at all. The scenario is about sales, not capital investment. The point is that its very unlikely (for retail at least) that you need to invest $X of capital in order to sell $X of merchandise. The question about returns here is not about returns on capital investment, but profit margins on sales.