Amazon very carefully tracks the profitability of each SKU they sell. If they're selling it to you, they've figured out how to do it profitably. Consider that you'd pay a similar price for it in a retail store, where it had to be handled multiple times, stocked on a shelf, subject to theft and loss, etc. - there's enough margin to cover that, so if Amazon can drop it in a box and ship it to you for less, they can make money on it.