Richard,

I think an important difference between "art photography" and "commercial photography" in terms of your post is that the "art print" is an object and the "commercial photo" is a service. An art object seems to be valued aesthetically and as an investment - some combination of these anyway. A hobbiest can easily move into selling some work if someone thinks it is good enough to buy. If it would "look nice over the sofa", (or "we should have that in our collection") that just might make the sale. Anyway the customer is buying a thing or object.

Commercial work is more of a "service" that at the lowest levels is not a lot different from paying to have your lawn cut, garbage hauled or leaves raked. Moving up the ladder, some commercial work might be equivalent to plumbing, auto repair, dentistry, requiring higher levels of skill, esthetics and knowledge on the part of the photographer. At its highest and best paid levels the commercial photography "service" approaches/assumes a postion of art. But the customers (at this point art directors, agencies and their clients) are still going to hire based on the apparent ability of the photographer to deliver the service they want. That service is a picture that sells bazillions of whatever it is they are selling.

At its base level there might not be that much difference between commercial photography and garbage hauling. Hauling garbage is not fun, cool or a pleasant hobby -- its just work and no one wants to haul your garbage for free. But photography is a fun, cool and pleasant hobby and people WILL do it for free or cheap.

The ability to deliver is underestimated by the unsophisticated client and is often completely overlooked when the price is low enough. There are plenty of photographers in the world scratching for a living. If a buyer has low standards and lots of vendors to choose from, prices will be held low.

I can not prove the amount of commodity photography thats been lost to improvements in technology but it is significant. Lots of the old bread and butter work is now easily done by a secretary with a digital camera. Perhaps not as well as it might have been done by a professional but its gets done and its cheap. Anyone who depended on this kind of work for a living is out of luck these days.

Anyway thats my rambling, semi-coherent take on the subject.