That's not what I'm talking about. Free software doesn't just kill duplicate effort. Free software kills the original effort that is there to be duplicated. You're saying "well all the unproductive leeches will go do something else". What actually happens is all the productive people go and do something else too.
If you fix the price of automobiles at zero, you don't get an automobile revolution that puts horse breeders out of business. You get an artificially created dark age while you wait a few extra decades for hobbyists to create the model t.