It's not a bad switch between the rock bucket and the standard bucket; it's going to be even easier now that I bought a quick-attach mount for the FEL (see attachment).
Cost? I'd guess around $1500; I traded my 60" rear-mounted snowthrower for it (with my gravel driveway I was tossing even more rocks where I didn't want them with the snowthrower!)
One rental place here has something they call a rock picker but only fits on a skid steer. Costs $385 to rent for a day. Personally I'm wanting to find a rock bucket that will fit on my Kubota LA402 FEL that doesn't cost a small fortune.
Personally I use the shanks on the box blade to rip em out, then I hit it with an old spring tooth harrow, let it get a good rain or two, to wash out whatever soil is there, and then rake with the stone rake.
I can’t believe that people want $1500 plus for these sifting buckets. I built one a couple of years ago to replace my pitchfork. There is not much to it. I used a used grader blade as the cutting blade and some angle and 5/8 rod for the tines. I should have used ¾” but they haven’t bent yet. The cutting edge cost about $18, the steel about $70, rust and overspray from using it as a saw horse while painting another project were free so I have a little less than a $100 into it and about ¾ of a day to build it.
I use this on my skid steer with the standard quick attach so it comes off and on in about 20 seconds. I have some similar questions as this poster about rock picking and pasture restoration but I will start another thread about my project. I’ll get some pictures of my sifting bucket soon.