Which, ironically, is exactly what a lot of people would have predicted had someone said Amazon should raise base pay to $15/hr.

They would have said margins are too thin, that it's impossible to pay more, that menial labor doesn't deserve more, that paying more would result in immediate widespread layoffs, that warehouse employees have little recourse but to accept their lot or quit because that's just how the market works.

But that argument assumes Amazon, or any business, pays some objective measure of what a job is "worth", or as much as the market will allow. They don't, they often pay as little as they can get away with.

So yes, Amazon could close down the shop, but Amazon could always close down the shop. They could also afford to pay their warehouse employees more. They don't, not because they can't, but because they prefer not to.