Except you don't need to buy decks, you want to. Food is something you need, and in that case it makes sense to look for the cheapest price, social responsibility be damned. But I can't think of a situation where someone might actually, really need a deck the way they need food. Decks are luxuries and should be treated as such.
And believe me when I say I am not privileged, I'm a graveyard shift, minimum wage security guard. True, I'm not responsible for feeding a family, but still I have never needed a deck, and there have been decks I have saved up for.
Again, nothing is black and white, I myself go buy luxuries in cheap places, too, because it means I can then afford more of other stuff, so I'm not labeling anyone who shops at Walmart or Goodwill selfish. I simply think awareness of these things is important.