Great find and lucky you!
I don't know why Kirbys are so cheap? They are like the Mercedes-Benzes of vacuums (this one is more like a Cadillac of its time). Dysons are like Audis and BMWs, sleek and high tech but will not last as long and are easily broken.
I can't believe I got a Sentria at Goodwill for only $20, including ALL of the attachments. It was in great condition with just slight oxidation. The aluminum polished up well. Nothing needed replacing other than the belt (I replaced the brushroll since I'm a germaphobe and brushrolls can't be washed). The fan was in great shape too.
An older Kirby should be going for a lot more than $8.82, and a Sentria at $20 is just wildly and ridiculously low, but I'm not complaining.