While they know they can sell some of the items, they've also opened a few of the boxes
Ojutai, Soul of Winter [Dragon]: Was occasionally useful when it was in standard
Dip into Mark Rosewaters Vision Design article, and youll find Silverquills student archetypes are listed as ROTC, mean girls, jocks, privileged kids, overachievers
The closest I could find to anybody doing it in the mainstream recently was Artifact (I know, I know, I'm stretching the word "mainstream" here) with a slightly bastardised version of the concept handled via Steam's marketplace, and even then it's still an online auction house, not just doing fun swaps with your pals and saying "well I've got this, what've you got?", like exchanging the best parts of your packed lunches at school
Mana Drain While this art technically appeared in Magic Online first, this is still astounding to see foiled in paper