How many of the same would an unskilled amateur be able to produce comparable results from?

If the user doesn't understand the work being done then at some point the skill is lost. If every coder alive simply stopped their studies then in order to properly know what was being output from the AI we would essentially need to reinvent the wheel.

Offloading human skills into a machine owned by a small group of absurdly wealthy individuals risks dependence on them. Long before AI systems existed we passed on skills and knowledge from master to apprentance (or whatever title is appropriate to a field) with the master supervising and correcting the work of the new workers. Forgoing that passage of learning by simply asking for a given result from a machine... I picture the scene from Idiocracy where a clerk is selecting from a picture menu at the hospital.