Pretty lucky.
'Got matched with a quality trading partner at random.'
'This is the great thing about trading with Extraterritorial Life.'
Sometimes, an item that's incredibly valuable in your own plane is quite common in another. This allows you to trade for something exceptionally precious to you at an extremely low price.
Of course, situations like this are quite rare.
Generally speaking, planes with an Eye of the World like the Dark Well are usually not too secluded; they typically have dealings with other planes.
Over time, the prices of items on that plane naturally align with the Multiverse, trending toward a normal rate. Finding another steal becomes basically impossible.
In this case, Pei Ze guessed that Tining had likely traded with Extraterritorial Life very rarely, which was why she had no clear concept of item values.
