Bill Erickson wrote a really great post in defense of consulting businesses. He lays out an extremely logical argument comparing consulting services to product services. The scalability opportunities for product businesses is an alluring one, so much so that I think (as does Bill) that many product sellers forget the support burden they can create for themselves, which can be just as concerning as the “selling time for money” concept often assigned to consultants.
I consider Bill to be the cream of the crop of freelance WordPress developers, and you really should read and digest his post if you are a WordPress professional of any sort. I especially love where he talks about how he justifies raising his prices every year, and why he chooses the type of work that he does.