These are my favorite containers, and have lasted me for many years. They are really thick plastic and come in literally any shape and size you could need. I use them for the things are out of season (currently they are full of ski clothes) and school supplies. They aren't particularly cheap but you only need to buy them once because they're definitely not going to break. AND they are clear which makes it so much nicer when you're scrambling to find something!
I have five of these that I used in my school closet for four years straight. These made my life a million times easier and gave me so much space, and now I'm going to use them at home too. I'm not kidding--these are one of the most practical purchases I have ever made. I seriously recommend them. They are indestructible and are a great option even if your clothes will be stored out in the open as long as you keep yourself organized!
These storage bags are awesome--great quality and very space efficient. I use these mostly for my towels, linens and other bed-related things that take up a lot of space. This way weight is minimized and they are easier to carry. I hate lugging bulky containers around when the things inside really aren't all that heavy, but I also want to make sure my things are protected from dust/moths, etc.
Anyways, those are a few of the reasons I LOVE the Container Store.
Completely unnecessary? Absolutely.