When I joined the ranks of pro photographers, it was much different than it is now. I bought a 35mm SLR camera, learned to be proficient at taking images that were in focus and properly exposed, got a mentor, served as an assistant, did weddings, bar mitzvahs, and headshots, and worked for peanuts while I learned.
I had a "day job" that allowed me to work almost for nothing, and I saved up my bucks and graduated to 2.25" cameras and film, paying over $1K per camera, and sometimes as much for a lens. This was in the 1980s. In the late '80s, I made enough to buy a large-format camera, a 4"X5" view camera and lens, and some studio strobes and I had to learn photography from another viewpoint - upside down and backwards. The barrier to entry was high: around $10K for the camera and lenses, and $5K for strobes and accessories. No amateurs need apply.
When we shot a wedding or a bar mitzvah for $300.00, we would show around 180 "proofs" out of the 210 medium format images we took. We would get substantially more from commercial clients, only managing to shoot 6 views of their architecture or product in a long, grueling day with the 4X5.
Fast-forward to today. A great wedding photographer friend of mine says no one will hire him unless he produces over 1,000 images at a wedding. Quantity prevails over quality. 12mpxl cameras (not necessarily good ones) can be had for as little as $99.99. Anyone can shoot an image and not even have to pay a lab to process the images (another barrier to entry bites the dust). Enough amateurs taking enough images may be able to duplicate the works of Ansell Adams. Most of these amateur images are sub-par - architecture with heavy shadow areas and no detail, images with no color, etc. Even with Photoshop (a rather expensive program, but affordable to anyone with an open credit card with a reasonable limit) most people don't know how to even crop an image properly. Yet, there are job sites that are looking for pro-style images who are offering less than $500.00 for 20-30 separate catalog images, and are taking bids. The lowest bid was at $125.00! The work would take several days, and I could make more working the counter at McDonalds. There's no way a "real pro" could justify taking that job.
The architectural photographers have been decimated as there is no money being lent by banks to start or even finish projects, and so there is no work for these photographers. To top it off, something hit the market about a year or two ago called HDR, or High Dynamic Range images. With proper software, a tripod, a static scene, and an adjustable DSLR, pretty detailed images can be taken with no lighting equipment and this has caused a huge drop in the pricing of exterior and interior imaging. I have seen 15 finished images promised for all of $115.00 on the 'net. Of course, there is a difference between an HDR image and a regular image shot with sufficient additional lighting, and that difference is usually extreme contrast, over-saturation, and sort of an illustration look. While no one was thrilled with paying us a lot of money for images, we worked our butts off, spent tremendous amounts of capital on equipment and training, and strived to get the best images possible.
Most of us have had to expand our capabilities or go back to work we had done in the past. For me, it was shooting products again. I was once so busy shooting and processing architectural images that I had no time for other forms of photography. I have since added food, and automotive to the mix, as well as assignment work. I continue to work for an ad company who works for a national bank and get out and do lifestyle images, and I also occasionally work for an environmental engineering firm. Some of the work is not pretty, but it pays the bills.
So, when all of us pros are gone, who will do the great still marketing images for advertisers and marketers? To quote John Arbuckle, "You get what you pay for."