Your expenses are too simplistic. Your cameras should be amortalized at 24 months due to increase technology. How long do your lenses last? You have to make enough to not only cover your expenses, supplies and bills, but also to make enough to replace or repair equipment as the need arises. How about transportation? Insurance? Computers & software? Business expansion? Batteries & Chargers? Lights & cords? Backdrops & sets?

Everytime I upgrade a camera, I get a larger file size. I then have to buy a new computer that is faster to handle the increased file size. I have to buy bigger hard drives to store my photos on. I also have to buy larger and faster compact flash cards. I have to buy upgrades of my software to run on the new computer. A new camera doesn't cost me just the price of the camera, but also everything else that is used to process, store, sell or print the photos. All of this costs money or in 2 years you find yourself outdated and out of money even if you are busy taking photos.

Photography business is 80-90% business and 10-20% photography. If you are a great business person and go into the photography business, you will probably be successful. If you are a great photographer and go into the photography business, you might be a good employee.