Huh? Wouldn't they have to depreciate it over several years so only a fraction of it would be a deduction in the current? Or is the idea that they'd buy so much capital equipment that even the fraction they could depreciate that year would wipe out all the other income?

AIUI, the concept of depreciation exists in tax law precisely to prevent indefinitely deferring taxes via reinvestment (though it can't do anything about the portion of reinvestment going to pay salaries a la Amazon):

https://hackernews.hn/item?id=15061439