Well from what I can see, the electric motor unit is direct drive so about 1800RPM input to the mill gearbox. The diesel run model is powered by a changfa diesel engine(pretty durable unit by most accounts). People take these and direct drive 4 pole 1800
RPM generator heads to make power plants. The belt drive from this engine to the mill gearbox in the E-bay pics shows nearly a 1:1 ratio, so again approx 1800
RPM into the mill on the diesel version. Since it is belt drive, that leads me to believe it has a fairly robust input bearing, so direct drive from a
PTO shaft would probably be no problem. But I havn't seen a pully side view to confirm if it has an outer support bearing along with the input pully. The
PTO version on the Pellet Pro site appears to be direct drive with no gears or pullies, at least as best I can tell from the small pic. It either has some different internal gears(unlikley IMO) or with 540
RPM input, it just runs at 1/3 the output capacity of the diesel version.
You will need a hammermill or some other form of material reduction to get the input material to less than 3MM-1/8" cube size.
Those lower prices on the E-bay auctions are FOB china. the price for the bare grinder for making your own
PTO powered unit is under $1000. But, that means you are the importer, and will pay all customs, dock, unloading, inspection, storage and longshoremans coffee and donut fees associated with it's delivery to tacoma WA. Plus any shipping from tacoma to your final destination, which is why pellet pro charges what they do.