Stereolithography is not an inexpensive process. The machines themselves usually cost in excess of $250,000. They have to be vented because of fumes created by the polymer and the solvents. The polymer itself is extremely expensive. CibaTool SL5170 resin, a common photopolymer used in stereolithography, typically costs about $800/gallon. For these reasons, it is uncommon to find stereolithography machines anywhere but in large companies.
However, there are service bureaus that can make the advantages of stereolithography available to smaller shops and individuals. For example, PT CAM will do stereolithography for $55/hour, as well as allowing companies to purchase blocks of time for as low as $30/hour. That's not cheap, but compared to purchasing your own SLA and resin or having parts machined, it is a real bargain. You can e-mail your CAD design to PT CAM and, in many cases, get your parts shipped back to you in a day or two. The short cycle time is one of the most appealing things about stereolithography!
Special thanks to Joel Leonard, Jerry Watkins and Steve Oneyear for their help in creating this article!