If you want to build and run a $70 million dark matter detector, you're going to have a hefty shopping list. You'll need to buy hundreds of photomultiplier tubes, set up elaborate electronics, and pay graduate students, for starters. And 20 percent of your cash is going to go to just one thing: xenon gas. You'll need 200 steel bottles of the stuff, purified from the Earth’s atmosphere, at a price that can fluctuate wildly around $100,000 a bottle.

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