Replace “cost” with “cost share” I think would help. But since there’s a hard limit on the number of passengers, it’s appropriate to make the division showing

Replace “cost” with “cost share” I think would help. But since there’s a hard limit on the number of passengers, it’s appropriate to make the division showing a best case scenario of gallons per passenger-mile, or in the terms of Bitcoin, kWh per transaction. If the number of passengers or transactions was unbounded, we could still say there’s a weighted average ROI in terms of passenger-miles or transactions carried on the bus / that were actually carried on the bus/block. Note that while the only utility of the bus is to carry passengers, blocks also distribute newly minted coins which is useful on its own right / even if the block is empty. The main point is that the energy usage is obscene not because it has to be, but because the simple economic function driven by the mechanics of the lottery — it must always balance the block reward against cost to participate in the lottery in a PoW system.