This is the impossible question. There is no formula to determine the answer.
The easy answer, if there is such a thing, is this: a photograph is worth whatever someone is willing to pay for it. Someone was willing to pay $4.3 million for Andreas Gursky's Rhein II.
I'm not really interested in easy answers, though. I want to know what the value of my photographs are. How do I price my images?
|Fireworks Over Mission Bay - San Diego, California|
The above image is one I recently sold.
A photograph is worth more if it cannot be replicated easily. There are millions of photographs of the Grand Canyon that pretty much look alike, and none of them are worth much. But if you have a unique photograph of the Grand Canyon--one that is different from the millions of look-alike photos--that image may be worth something. If a photograph can easily be copied by other photographers, it likely isn't worth a whole lot. If it would be difficult for other photographers to copy what you created, then your photograph is likely worth something.
Another thought on scarcity is that if you are the first to create a certain photographic look, even if it can be easily replicated, it may be valuable until all the copycats come along and rip off your art. There are trendsetters that make a career riding that wave.
If a photograph is needed immediately, it's worth something. Perhaps you are one of only a few people who have an image of some breaking news--that photograph is likely valuable. It may be an image you wouldn't be able to sell otherwise. But you were in the right place at the right time to capture it, and now someone wants to print it.
Quality is an essential element to the value of a photograph (aside from immediacy, in which case quality may not matter). Your photographs must be high quality in order to sell them. The higher the quality, the more they're worth. I'm not talking about equipment when I'm talking about quality. Sometimes equipment equals quality, but typically not. Quality starts in the mind and heart of the photographer. Vision is quality.
The final element that determines the value of a photograph is name. If you are a well known photographer and your name is easily recognizable, you can demand more money from your images. That's the case with Gursky's Rhein II mentioned above. If I had made that exact same photograph, it would not have sold for millions of dollars. Your reputation--and whether or not you have a reputation--plays a large part in determining how much you can sell your images for.
When trying to figure out the value of a photograph and what you should sell it for, consider if it can be easily replicated, if it is immediately needed, if it is high quality, and what (if anything) your reputation demands.
After that, it goes back to the easy answer: you can only sell it for what someone is willing to pay for it. Figuring out what someone is willing to pay for something takes trial-and-error, time, experience and luck. My advice is to start high--the worst anyone will say is no. As you work your prices down you'll discover what people are willing to pay. For each photographer it will be different depending on a whole host of factors.