A sled from Reliable is $900, and I'd take that over the Aigner any day. Pneumatic clamp, and it pumps air through through the base so it's riding on air. We run them in the mitre slots and you'd really have to be trying to get hurt by the cutter. (Though I have had two guys think it was a good idea to clamp their fingers down, then try and pull their finger out before releasing the clamp) Some people don't listen when you tell them it'll be painful.
I agree with Mark though, anything you can take the operator out of the equation, you're better off. PMK has a coper/tenoner that I'm hoping we can acquire in the next year or so. The operator just needs to load and unload the parts, the rest is automated, runs two rails at a time, and it doesn't need a backer to prevent tear out.