To put some weight behind the quote from Andrew McAfee's quote (“The opportunity is massive,” said Andrew McAfee, a principal research scientist at the M.I.T. Center for Digital Business. “There are still people who walk around in factories and pick things up in distribution centers and work in the back rooms of grocery stores.”), just the external logistics of the Supply Chain of modern businesses accounts for around 7-9% of the GDP[1]. In developing countries, it is much higher (although I don't have a non-gated reference for other developing countries, the link in [1] shows China's cost at 18%). Interestingly, while inventory holding costs are included in that estimate, internal fulfillment costs (think Pick and Pack, Rail Shunt Yards, Crossdocking, etc) is not included as that is typically considered an operations cost. Those costs vary wildly by industry, but I can imagine it tacks on another 20-30% on top of that.

This would mean that the modern industrial supply chain costs the US around $1.5 trillion/yr.

[1] http://www.kpmg.com.cn/en/virtual_library/Property_Infrastru...