Prices for used Wii Us are around 200 EUR in my region. I'd say that's not a bargain and makes the idea of a new Switch for an extra 100 bucks way more attractive.
The snark is unnecessary. Of course they exist. Whether they are "dirt cheap" and whether the associated trade-off in quality expectations is worthwhile are entirely legitimate debates.
For example, I saw refurbished Wii U consoles for $200 the other day, and I'd be hesitant to spend $100 or $150 on a device with no warranty. But for $200 it's not crazy to think you might as well go for the Switch at $100 more.