Getting food locally delivered is far less energy efficient than having it shipped in bulk by freight to supermarkets.
Bottom line the world is running out of hydrocarbons. Things that look "energy efficient" to you today won't look so efficient in 50 or so years. Peak oil already happened in the United States, Hubert's peak is reasonably well accepted, and the idea that shipping food thousands of miles is a long term sustainable strategy for feeding humanity or that the entire world can live like the people in Silicon Valley and New York City is laughable.
That is my last comment on HN - mods, please prove my point by voting it down.
Some on-topic points:
1. Energy efficiency in terms of joules per kilogram per kilometer is a constant, regardless of the actual dollar cost of the fuel.
2. 50 years is a very long time to come up with the technology to replace fossil fuels, hopefully with cheap fission and eventually fusion.
3. Modern civilization thrives on being able to disregard geographic barriers. We could never have a global society if transportation of physical goods became impossible. So, since we (as a society) won't accept the defeat of modern civilization, we will simply find another way to continue to exist. If that means replacing fossil fuels, then it will happen.