Imagine if you had a rich uncle to float your retail business? Amazon didn't start out with one, but now it has one via its cloud computing service. The cloud computing service had an operating profit margin of 23% while its retail segment had a rate of 2%. Essentially, Amazon is selling retail stuff at close to a loss - a practice few retailers would pursue. But if one makes a 23% profit on other stuff, it can afford to. Competing against a 'store' with a rich uncle is not fun.