You can get a brand new Precision Matthews mill for $5400. Add another $600 or so for accessories that would match the one you're looking at, plus about $500 for delivery and you're at $6500.
He may have sold the last one for $4950, but what was the asking price? Go there in person with money and all your tools to check it. Tell him you're willing to travel to save a few thousand dollars. Ask them what their best price is and see if they come down, or how much they come down. I've found if you stay and chat and are friendly and let them know you're serious you can glean bits of info that will inform your offer.
He's local, but you still have to get the mill to your shop. Not sure what it costs to get a mill delivered, but it would be worth looking into so you know if you're saving any money by looking close, or if the cost is based on something besides mileage, or if mileage is a small part of the overall cost.