Stock photography is an excellent resource to designers because we don’t always have the time or outlets to take our own pictures or hire a photographer. When I was just beginning as a designer and visiting these stock photography websites, I could not understand why royalty-free photos were not actually free of charge. I finally had to research the meaning and discovered that you still have to pay the price of the picture, but it’s only a one time fee. After you pay, you are able to use the photo multiple times, hence free of royalties (although there are still restrictions for non-commercial use, etc.), as opposed to the “Rights-Managed Licensed” photos where you are basically paying the person who took it and you pay every time you use the picture. The Rights Managed photos do allow for a much larger print though.
At the moment, I have a membership with iStockphoto which gives a relatively good selection of royalty-free photos, vector illustrations, and royalty-free videos for a reasonable price. A low-resolution image for websites costs $1-$3, as opposed to a royalty-free image on Jupiterimages.com, close to the same size, can cost about $100. It just depends on the quality and selection of photos you need.
www.jupiterimages.com is a good source for more professional-looking photos with an enormous selection
www.istockphoto.com is a better source for cheaper photos with a decent selection.