I have had the same $10 Wal-Mart cooking knife for a few years now. I'm sure it won't last more than a few more years. However, I bought it in poverty, and it will last me through poverty until I am making good money. Then I will buy a nice knife. There is nothing wrong with that.
Grad school is hard. It requires a lot of my time. A sewing kit is not cheap, and sewing is time-expensive. It is probably a net positive for me to throw out socks with holes in them, even if they cost me a few extra dollars over the course of three or four years.
I understand the urge to simplify. This is the land of Henry David Thoreau, after all. But sometimes it carries an assumed moral tone without justification. People feel it's right and don't question it. If nobody bought from Wal-Mart, people would have a lot less stuff. Some of that stuff is valuable, it saves people time and makes them more comfortable. Often cheap stuff is bridging a gap for folks caught in hard times. There is no need to moralize against them.