That's got nothing to do with free trade, what your talking about is Supply Chain Diversification and Strategic Sourcing. The emphasis is that price is only one factor, speed of delivery, identifying alternate sources, securing the necessary import/export paperwork in advance, risks and other factors are considered to ensure that a company does not run the risk of being over exposed to a single market.
To give you an example of proper supply chain management. I buy sprockets from a supplier in Country B for 10p each, they take two weeks to arrive and the country has an antagonistic neighbour who may blockade it. I also source a small amount of my stock from a local supplier in Country A to keep them in production, they cost 15p each but they only take a day to arrive and I can surge my order to a limited degree if I suddenly got a large order or if something happened to my supplier in Country B they can tide me over for a short time. I also have an agreement with a supplier in country C. They can start supplying me as many as I need with four weeks notice but they will cost 12p. I am therefore covered against risk to my suppliers and able to meet unexpected demand.
Some companies like Toyota take this to extremes, they essentially maintain rather than limited number of suppliers and centralised production plant an internal market for supply and production, a hundred subsidiary workshops of varying size from man in a shed up to virtually unlimited production capacity factory that compete against each other for orders from a central procurer. It keeps the prices low through competition, keeps production dynamic, encourages innovation and allows work to quickly shift and gear up or down to meet demand.