Good morning, wknox! Welcome.
Until I saw 77,000 miles, my response would be somewhere from $2,900 to perhaps $3,300. That's a lot of miles, so a lot depends on how much you know, or how much the current owner can document, the service history.
My 2002 had 6,600 miles when I bought it "as is" less than six months ago, and I knew nothing of its maintenance history. Perhaps I took a gamble, but I also paid very little (below the range I mentioned above) and decided that, even if it was poorly maintained, the number of miles on the bike reduced the odds that poor maintenance had resulted in permanent damage.
If this bike was poorly maintained, 77,000 is a lot of miles for related problems to accumulate. If the Swing was regularly maintained and is currently in relatively decent shape, you may have found a gem. Personally, I would look to pay less than $2,500, probably closer to $2,000. But I certainly wouldn't reject it simply because of the the odometer reading.