Trading going on

The new thing with E + E is that they do a lot of trading. There is an imbalance that I'm not comfortable with, also being the youngest child in my family. For instance, today I went to pick up the room, after the children took their turn at "cleaning" . Eva had Eli's big treasure trunk moved near the book shelf. I asked her why Eli's box was there. She explained that they'd traded. He got a coconut shell from last summer from the Costco frozen desserts Syd/Sean brought to North Garden, plus some gravel that was excavated from Shu Shu's driveway. She also said that she got all the treasures inside the box and that Eli has relinquished his rights to the books and they were now her library. It is difficult for me not to step in and defend Eli but I bit my tongue...