This idea kinda goes against the concept that houses pay more for unrefined minerals to keep the labor costs in-house. Better idea? Have the modules create high-quality metals that are used in the production of ship equipment instead of hundreds of thousands of regular commodities.
Better yet, make it so, for example, high-quality super alloy would count for several units of the regular stuff when building base modules or equipment, similar to how different fuels are consumed at different rates based on quality.
This would give your idea purpose beyond just making money. It would promote player interaction, and perhaps provide a way to get certain goods more easily depending on location.
It would also give bases a purpose beyond just being high tech equipment factories. What business does, for example, a KM base have producing cloaks?