In a "free" market why would a Bulgarian be forced to operate only near Bulgaria?

As an example, all food in Romania is from the Netherlands or other foreign countries. But you don't see the EU imposing regulations to make foreign food more expensive.

Essentially eastern Europe is an exploitation market: everything is manufactured in the west, and when the east has an advantage it's immediately shut down.

This is also very polluting: forcing eastern European drivers to migrate to their home countries frequently, transporting food from western Europe to eastern Europe.