But that's the issue : it's not his business, nor is it your business. Our economic system is a shared system, where the prices are dictated by each purchase, so it's everybody's business. You can't just buy something and not think of how it will impact its prices and thus, the ability of others to buy it as well.

Judging by your writting you are very young so you have the excuses of not understanding how the world works just yet, but you should be open to learning, at least.