Why not get a auto towing company with one of those ubiquitious Jerr-Dan flatbed car haulers to haul the disk? I bought a 10' bushhog a few years ago about 20 miles from my home. I got a guy with one of those Jerr-Dan rigs to pick it up and deliver it...the price was quite reasonable.
Line up the hauler, go make the deal and don't offer any information that would entice the seller to raise or not negotiate the price. Once the deal is made, call the hauler and your problem is solved.