In my area they're pretty much the same price as side pull balers. Not as many used though for sure.
I've been running one for about 12 years now. Won't go back. Square bale every time regardless of windrow size or any other variable. Simple, equal weight distribution, safer and easier going down the road and I can load it on a trailer and move it with ease. That's big for me as I have fields 10-15 miles away and don't want to run my tractors and equipment down the road.