Some import products are crazy cheap because cross-planet shipping is basically free because it's the reverse end of a trip carrying valuable stuff. But they mainly applies to ships returning from low development level regions.
While the majority is bulk, the US does export a lot of industrial machinery. It's just not stuff you normally think about - like the large hvac systems on the roof of large buildings or the caterpillar earth moving equipment/parts to make roads.
Some import products are crazy cheap because cross-planet shipping is basically free because it's the reverse end of a trip carrying valuable stuff. But they mainly applies to ships returning from low development level regions.