I learned something like this a few years ago when I was a contractor. If the skills I had were in the job description (e.g. "C# programmer wanted! Need someone experienced with embedded systems!"), I charged myself at fairly high rate. If the job I was applying for didn't specify the skills (e.g. "I want someone to program a cell phone application."), I charged a lower rate.
Invariably, the person who knew the exact technical skills they were looking for was willing to pay more for those skills than the person that knew what they wanted, but didn't know what went into making it.