The purpose of your images should always be to increase sales. They should be eye-catching, convey quality and create desire.
Unfortunately, many professional photographers, graphic designers, creative directors and ad agencies just don't get it. They get so caught up in their desire to "be creative", win an award or copy the latest fad that they totally miss the point. They forget that the whole reason they're hired is to increase sales.
Buyers are bombarded with information, overworked and more than a little busy. They'll search for a particular product or service and they'll compare your website or brochure with your competitors. Most will quickly scan your materials and look at the photos to get a feel for the quality of your company and what you're selling.
Because we think in pictures (think of your car - does an image come into thought or do words?), images influence perceptions. You'd better have images that convey quality, create desire and build trust. Images that are at least as good as your major competitors and preferably better.
The photos you use create powerful perceptions of your products or service. High quality professional photos provide a great return on your investment through increased sales.
Images that aren't high quality create the perception of an second rate company and cheap products. The money you think you're saving is small compared to the sales you'll lose.
Images that increase sales will return profits that far exceed their modest cost. Cheap shots will cause you to lose sales without you even knowing it.