Your model feels trueish to me, but I think the analogy is actually overcomplicating it. The basic nature of finance is that some people have money they don't

Your model feels trueish to me, but I think the analogy is actually overcomplicating it. The basic nature of finance is that some people have money they don't immediately need and others have needs they can afford over time but not upfront. It's basically a layer on top of money in general, which is a way of decentralizing value production. Instead of pairwise trades, money serves as credit for value creation, recognized by 3rd parties. The people running the graph are everyone with excess money or the ability to acquire it. Basically, everyone but the poor.