If my prices aren't too high, then what am I doing wrong?
It's not that you're actively doing anything wrong it's merely the market. People want everything for nothing. I've seen people shop at Wal-Mart for $1 items only to return them because they weren't the quality they were expecting. Society, blah.
I used to work in creative teams, and I've worked with colleagues who charge £500 a day in the UK. A lot of the value comes in not only the design, but how he packages it up.
(Just looked at your portfolio. I'd say your prices are good).