While reading In an Absent Dream, I'd wondered what happened to Mockery. This addition ties up the lose ends of the novella well and answers the question of what happened to Lundy and her friends that made her return to the world of her birth for the first time. The Goblin Market is a complicated place. It's not made for everyone to live in, and it's not made for everyone compatible with it to live in forever. This side quest explores how sometimes the concept of fair value can lose its meaning when an individual loses themself, and it shows the cost of a life lost in the "eye for an eye" fairness of the market. They're children with minds full of adventure and a strong belief that the market would protect them. It's also interesting to see more of the archivist as a person who can and does fail in her overseeing of The Goblin Market. 
On a related note, the concept of fair value has infiltrated my subconscious. I consider purchases and trades under the idea of "is the price of this worth the amount of time it took me to make the amount of money I'd used to purchase it," and "are the items we're trading worth the same value we're willing to take/share." It makes purchasing and bartering more fun, and I wish I lived in a place where bartering was more prevalent.