[thaumasiotes]

This does not reflect any understanding of taxes before, say, the 19th or 20th century.

Hammurabi certainly didn't devote his funds to public health care or public education. Infrastructure, yes. R&D... probably not. Monuments, public religion, and the military would have figured in his budget.

What you get back from taxes is stability. If robber barons kept ships from being attacked (other than by themselves) along their stretch of the river, they were fulfilling the necessary function of a taxing agent.