I use mine all the time. I paid $20 for from a quilt show vender. I peeled off the label and discovered it was a Wahl trimmer. I went to Walmart and looked at the razors and they were around the same price. Then I went over to the pet department and they had them for $8.97. That was a few years ago so I don't know if the price is the same. It's worth checking out.
I found that if you use it on an ironing pad or some other non-slick surface and anchor the bottom piece down with one hand or pin then it will cut the threads better.