Transportation isn't always about the cost, it has a major impact on the quality of the food too. Not only is shipped food less fresh but it requires plant varieties that are hardy enough to withstand the trip, and often means produce is picked before it's quite ripe. I dare you to find a tomato from the most tomato-friendly part of the world that is better than a locally grown heirloom.
That actually has nothing to do with transportation per-se, and everything to do with stores liking to be able to store products before selling them.
If anything eat local makes that worse, since there is a very very short timeframe where the food is ripe, so you need long storing food even more than before.
With remote shipping you can rotate around the world and have crops ripen all the way around the year, so less storage is needed.
It's not hard when you consider regions where basically nothing grows well.
I'm pretty sure tomatos from averagely tomato-friendly part of the world are better than whatever you grow in my local darkness and rain. Not to mention winter.
People in worse climates are already behind when it comes to quality of life, and suggesting them to eat local is to suggest them to further lose their quality of life voluntarily.
