"Unlike other economic activities, the bitcoin scheme produces absolutely nothing for all this waste. It is a pure speculative activity of people gambling on the random movements of prices and the only output is simply shuffling numbers around in a computer at insane cost."
Two things, my salary and expenditure are just numbers in a computer.
"insane cost" is also more numbers in computers, big ones that we collectively agree on being big.
Resource consumption, definitely, but if energy was cheap and prolific, the limit would be the cost (more esoteric numbers!) of the technology and its production, and consumption of material resources.