To the "is this guy nuts?!" part, not the "is the wheel worth this?".
I wouldn't pay more than $150 for a wheel that comes with a tire. Just a rim with rusted spokes? No way.
Just googling "1976 GL1000 rear wheel" brought up this: https://www.ebay.com/itm/like/3515106454 ... noapp=true
Same rim, plus the brake disc and a tire, no rust, less than half the price.