If you have a well written collection of patterns, then you can do well.
But please make sure that your patterns are well written and tested and follow the standards published by the Craft Yarn Council
http://www.craftyarncouncil.com/standards.htmlOnce the patterns are written and tested you can do quite well but getting them ready can take quite a bit of time and $$.
For example, after I've worked the design for each of my patterns and worked through it a number of times I'll hand it off to a group of paid testers to do a thorough test. I'll review the test results, tweak the patterns and then send them to my proof readers.
Then its time for the photos and the final assembly.
Yes I pay my testers because they are working for me and providing me with a service.
So yes a pattern may sell for $5.00 but there is a lot of work that goes on behind the scenes.