"I don't buy patterns because I can get them for free." -customer comments
Just a reminder, free patterns are great but they are not always test knit, therefore you sometimes need to make adjustments. Free patterns are often an advertisement or a way for a new designer to try out his/her ideas before deciding to make pattern writing a profession. When someone charges for their patterns they have put in time and money to have other people try out or test knit/crochet their designs to get some of the bugs out before it gets to you. They also spend hours worth of time formatting, taking pictures, and tweaking their design so you get value from buying the pattern. Often they are also available to help with misunderstandings and errata if it is needed. Writing a paid-for pattern can take twice if not three times as long and making the item itself.
Buying patterns helps support designers!