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Comment by lewis500 | Hacker News Reader

About 1.5 aircraft carriers or 3 bay bridge eastern span replacements. I have various costs in my head to conceptualize how much things cost in terms of what we could’ve bought. The last aircraft carrier the US bought cost about $13 billion. The bay bridge eastern span cost 6.4 billion.

For smaller costs a good one is submarines: about $2.4 billion.

I did the math once and the war in Iraq directly cost about the replacement value of the nyc subway but can’t recall the figures well.

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I'm not sure how the military devices help understand those numbers much. Presumably, the idea is to take something whose impact is large and intuitively understood and identify it with the price, so that other things which are nonintuitive with similarly large prices can be understood. (My preferred version of this is "$1M is about the life's work of a median American", in the sense of being the median salary over a lifetime minus what a human needs to survive. $1M is a lot of money, but I can kind of imagine what a man can build in his life.)

But military devices seem like things whose value is very unintuitive. (I've made similar criticism of people who say "oh, $6B? That's just three B2 bombers.") Obviously, we have no real conception of how complicated and expensive such devices are to build. But more importantly, few of us have a good grasp of the value to world stability delivered by rarely-used weapons that play a mostly deterrent role.

I think the main takeaway is how small this sums are when put in perspective of defense spending. Priorities.

Actually military figures are fine for this expenditure because they are very large per unit, so easy to conceptualize in small integers. It doesn’t matter if you can think about how complicated they are to build or their deterrent role or whatever. Point is you can imagine an aircraft carrier. This is about as expensive as 1.5 aircraft carriers or three bay bridge replacements.

If you aren't bothering with an interpretation in terms of value, and are just using the military device as a physical object you can visualize, why not just use "stack of 10 billion dollar bills" as a unit? Then you can think of the subway upgrade as two of those.

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