A quick search shows I can get fridges used for less than that in London, though mostly small ones. I guess to a lot of people, when they replace goods like that, the hassle of selling it outweighs the perceived return

No, you didn't. Says 10,000 yen, so about 70USD at the moment.

I can buy used fridges all day long for €50. I've gotten fridges for free that were still good for years after that.

No one wants used white goods. Fridges, washing machines and dishwashers you can pick up below $100 easily.