That's more than 10 times what Amazon paid for Zappos, its prior top acquisition, in 2009. It underscores just how seriously Amazon values its future role in the grocery business.

By purchasing Whole Foods, Amazon buys its way into a business it's long been trying to crack, sets itself in a much stronger position for online grocery sales, and acquires 460-plus retail stores that can be used for an assortment of operational purchases, from holding delivery lockers to becoming distribution centers for food deliveries.

The grocery business is a more than $600 billion a year industry in the US alone. And the industry isn't very concentrated. Aside from Walmart, which controls close to a fifth of all food and beverage sales according to figures assembled by Bloomberg, no other grocery chain has more than a tenth of the market. Only three others manage to grab more than 5 percent of total sales.