What it means is that once you have paid, the seller is compelled to consumate the sale. So if you want something, pay for it. That is how the current systems are designed. Is that more clear?
Had you paid, in all likelihood you would be listening to your subwoofer rather than questioning the moral compass of your seller. This in no way is meant to justify any behaviors; it is meant to explain, how as a buyer, you have the ability to shape the outcome of the sale.

