Much. To me, the thing that really needs to be more realistically considered is interplanetary (not interstellar) trade. Lightspeed-grade goods and services (me

Much. To me, the thing that really needs to be more realistically considered is interplanetary (not interstellar) trade. Lightspeed-grade goods and services (media, data) have one "cost," and inorganic atomic-structure goods and services (gaseous/liquid/solid matter) have another "cost", and organic biological matter — especially living matter — will have an even greater cost still. Getting information to Mars will be far cheaper in energy and currency than getting a crate of parts there; and that will be far cheaper still than getting humans or their biological foodstuffs back-and-forth.