Even the extremely rare Onyx isn’t worth nearly as much as this. The problem is trying to find one of these. Not only do you have to work through rod upgrades but then also have great patience in waiting to actually catch one, and hopefully it’s a big one. This took a long time.
Merch - https://df.store/
Game: https://store.steampowered.com/app/1106840/Hydroneer/