The First Was the Best:
It was (and still is; I still own it) a Lux Diamond Jubilee, with hose and the correct PN-5, for $2.02.
It was the worst-clogged machine I've ever dealt with, and I was afraid of motor damage because of how badly it had been treated, but once it was clean, it ran like new, without complaint, and has ever since. Incredible suction, especially for a Lux.
I have better vacuums now, and more collectible ones, but the DJ is the highest value in proportion to purchase price I've ever achieved.