I'm assuming you are talking about the hand held ones. The first time I saw one was a couple of years ago. We were on vacation in Gatlinburg and visited a quilt shop. The husband used one to cut my fabrics. It did cut likety split! The owner said they had purchased it at a trade show and it was over $300 but both he and she said that was cheaper than the self healing mats they were constantly replacing. I saw one being used by one of the designers on the show Project Runway All Stars this past season. The other designers were unimpressed with it.
If you are talking about the Simplicity Rotary Cutter, don't waste your money. Do a search here on the board; many negative reviews. I had one that I got as a gift when they first came out. I couldn't cut a straight strip with it to save my soul.