At least in financial markets, it seems that over time, it has only become easier and cheaper for people with less money to purchase liquidity and participate o

At least in financial markets, it seems that over time, it has only become easier and cheaper for people with less money to purchase liquidity and participate on demand in some of the same markets as wealthy people. While there still are people who are too stricken by poverty to participate, the threshold of participation is getting lower -- which seems to stand in contrast to your claims. On the other hand, there definitely are other forms of exchange, say like dark pools, where wealth and status are required to gain access. I think I would hold out for a model that was able to work with actual transaction data like this, rather than needing the mathematical conveniences of the paper (that only budgets are limiting, that transaction network is the fully connected graph of all participants, etc). It's good work, I hope to see it keep going and go in a more data-driven way.