Picked it up this weekend for $500. 1985 Interstate with 70k km. The owner bought it in 1986, and has had it since (I'm pretty sure I saw tears, as we drove away with it). It's visually well cared for, and mechanically sound (mostly). Bad fuel, misadjusted idle and low clutch fluid were messing with me this weekend, but I got it sorted out. It idles properly and pulls hard now.
It has an exhaust leak, broken speedo cable, bald rear tires and the fork oil is probably tar, but I'll get that all fixed over the winter.