I bought one after a drunk driver nailed me and did 20G damage to my truck.
Yeah I know, kinda like closing the barn door after the horse runs away... But just in case....
So I have one now that records everything that goes on in front of me. I may never need it, but what if I do?
I paid 100 bucks for mine. Not the best unit, but there is now video evidence of my every move, as seen out my windshield.
I think they are an essential thing for us. It never ceases to amaze me how some clown thinks it is his mission to cut me off and do a quick turn, standing on the brakes, thinking that my 15000 plus pound rig can stop on a dime.
A lot of idiots out there.