"Who would even buy such a thing for 10 silver?"
"600,000 silver!"
I have seen this thing before in manga, for example in "An Archdemon's Dilemma: How to Love Your Elf Bride". Someone suddenly offers a totally unnecessary, astronomical sum at an auction. It must be some kind of Japanese cultural thing of wanting to show off, regardless of how stupid or needless it was. I might be remembering it wrong, but my gut feeling is that in wuxia/xianxia, which are obsessed with auctions, the Chinese authors usually don't write it like that. Rather, the characters either just try to beat the competition normally or even try to intimidate the competition to drop out, so that they wouldn't need to waste money (or whatever resources are used as currency).
It's almost like a portion of Japanese authors don't even understand how auctions are supposed to work, unless it's indeed cultural for Japan. If it is, then certainly anyone wanting to sell some treasures of theirs and if at all relevant, they should consider doing it in Japan.