I'm just getting into this hobby, but I've also noticed that the prices people are asking for vintage vacuums is absolutely INSANE. It's discouraging. Sellers on eBay are definitely smoking something. I was VERY lucky apparently to get my Electrolux vacuums fairly cheap.
Although I've also noticed that antiques in general have really gone up in value. I collect other kinds of antiques - mostly cameras and typewriters. Years ago, I used to practically trip over typewriters in antique and thrift shops, but for a while more recently they suddenly became much harder to find and were selling at nutty prices. They're starting to come back down to a little more reasonable prices, but still not as easy to find as they used to be. I don't know what's going on...maybe hipsters buying stuff to brag how "retro" they are and jacking up prices? On one hand, it's good that people are interested in antiques...but as a consequence it is making things harder for hobbyists.