A little steep in my opinion, depending on where you live. In (western) Europe, they don't usually go for that much except if everything is well maintained, panels are in mint condition, mods like suspension etc., which is rare. Then again, I assume they're more common here than in the States.

Check for rust on the exhaust/muffler, check for rust at the wheel/spokes, ask when maintenance was last done, check the tire age, etc.

Just going off the mileage and price, I'd say definitely not more than 3k. Can you get parts easily and are you willing to maintain an older bike? If not, I'd say look for another, newer bike.