Hanging file folders with box-bottom?

Do any business-type BOTLs use these in their filing cabinets? I'm a writer and I have a lot of rough drafts I want to catalog. I just bought a filing cabinet from Staples, but forgot to grab folders. What's a cheap site some of you might use to buy assorted-color box-bottom folders?

Those are the ones that instead of having a V bottom like a manila folder, are built like an open-ended rectangle, to allow for more, sturdier storage. I'm looking, but the closest I'm at at the moment is OfficeMax for $27/25. Seems awful high to me.

Help is appreciate, please and thank you.

Kegan