Occasionally we need a specific type of pattern - for a class, event, to showcase a particular yarn or stitch - and so we play around and create one. Many of them are free because we simply "Do the math" and don't really view it as a pattern per se. Others have a nominal fee because they have been test knit and/or edited.
Please note that our low cost and lack of fees is not an indication or comment on other designers pricing structures. We truly believe in paying designers for their work. It's very difficult to design, grade, edit, and produce a workable pattern. Patterns are intellectual property and the creators should be paid for their efforts. Again, our pricing structure reflects the complexity of the pattern - if it's simply using a stitch pattern or was created as a give-away for an event, I don't feel obligated to charge for it now.