I've two Kenwood chefs (with lots of the accessories too) - one is a spare, the other in full use by swmbo'd.
Just moved home and it required two very full 18 tonners - and am now settled into the Forest of Dean in a village where there are plenty of old car nuts, but the Forest has been known for eccentricity.
back on topic, Alan is right, buy when unfashionable and hope it comes into fashion!
My best buy ever, one item purchased for £24, sold for £6700 - and, no, it wasn't a car!
Thing is, our cars are fashionable now - that was something that started in the mid 1980s when all sorts of 50s and 60s stuff was to be found in scrapyards - none had microcars, as they had all been spirited away. By the late 1980s, prices were on the rise and a Messerschmitt in good condition was still £1500-2000 then, so is the £15-25k now unreasonable?
People like microcars, you only have to take one to a show to find that out. That popularity equates to demand which, in a finite market, means people pay more.
The market is also global, with collectors the world over wanting to have the unusual and quirky. Expect more to be exported! SO why not do a trade the other way - leboncoin is good for French cars, the distance is not huge and you have something quirky, fun and rare in this country. However, the bottom line is lots of our cars, beyond the few mass produced cars like Googo, Messerschmitt, isetta, were rare even when new and produced in low quantities, making them rarer still today. There are 156 Tigers, but perhaps ten or twenty Inters, a few Reyonnah, one original Isetta pick up, one Messerschmitt Kr201 Sport, one Mi Val, etc.
I'm glad I bought my cars when I did, I couldn't afford them now, nor would I pay the prices. But they are like your house - the money is not realisable unless you want to sell. I don't want to sell and consider my Schmitt of no value as I have no intention of selling it. However, I know what it is worth (ditto the house), but would rather have the car than the cash (or a nice house, rather than rent).
Get used to the high prices and the new collectors - they're here to stay, unfortunately.
This is a blip - the prices were astronomical, as they were in 1997, but the market stabilised afterwards then and saw a steady but slow creep up in prices. as there has been in almost all classic cars.