I think I finally get it now!! I thought it was a "ruler"!!
One edge of the gripper grips the ruler you are using to measure and cut with, the other edge of gripper grips your cutting mat OFF the fabric. You hold on to the gripper, not the ruler. So yes, I can see where this is both a safer device and if it grips and holds like everyone says, a more accurate device than most I've seen for keeping my ruler in one place.
For SueSew ... your left hand will be on the wooden handle of the gripper which is several inches to the left and ABOVE your ruler edge (this is assuming your rotary cutting with your right hand). So unless you have a seizure of some type and your rotary cutter flies up and over ... I don't see how you can cut yourself with this thing.
As for cost justification, I would want to see it, hold it, touch it, and try it before spending that much money on it. I'll want to make sure it's comfortable to use, easy to adjust in micro increments, easy to pick up and move to the next cut, etc. It's not something I would buy online sight unseen, at least not at that price.