I shot on Lubitels for as long as I can remember, which is mid-1970s. They are fun, the shutter lasts a year or so then you throw them in the landfill and buy a new one for £12. When I saw the price being asked now I assumed it was a joke. As for Diana's, my friend shot on them more than 30 years ago. He'd buy six at a time to get a good one, from the kind of places that sold water pistols, fart powder and rubber spiders. He was really cheesed off when they hit £1.99.
You can buy a nice German folder for £20 and experiment with Vaseline and filters to your heart's content if pictorialism is your thing. For the price of a plastic Lubitel you could buy a used 5 x 4 in good condition. There's something very wrong with that.