You can try to improve that model, but I would bet that you will get rising inequality as well, it will just be masked by the growth ad infinitum. And unlike in the Norvig's model, in your model the inequality will not be bounded.

Of course, in the real world, people need upkeep (which could be modeled as a fixed amount subtracting from their wealth over time). So not all transactions are net positive, because at some point you have no choice as to whether or not to buy food. Which would even exacerbate the effects of inequality for low income people.