This is not correct, the ancient world and the ancient Mediterranean especially saw food get transported by sea. Rome.had to import much of it's food, for instance, as did Athens.
Well you're not wrong, but that was still the exception, and on a smaller scale. So maybe food wasn't the best example to get my point across. Like you said, they had to, it's not like some clever Roman said "hey you know what, I'll just buy cheap stuff from overseas to make more money and then fuck our farmers." Nobody sent locally harvested produce for processing to a country half around the world and then back. Or look at when ancient Rome and China did trade. That was for luxury goods, not for basic household items the average Joe would buy.