Yankee: As a general rule, the docs will tell you what is possible but won't outline a strategy. For example, the mechanics of moving stuff across space is there but it won't tell you for what reasons you may wish to do this. So, I will point out the easiest, and less well-known method, to trade across multiple worlds and touch on the obvious way.
The first way, and easiest, is through direct trade. Using the function "exchange products with countries and enterprises" you can move any 16 products instantly to your account and back again to any entity you own. You can obviously sell these for coins in the direct trade area or simply move those products again to any world that may offer a better market price for such products. All of this can be done without owning a single shuttle.
The other way is using the space game. Getting into it for premium members is actually quite inexpensive, with a small fleet of shuttles available on direct trade for just a few coins. Small fortunes can be had checking the markets of worlds you reside on and purchasing things on sale to hold for awhile or transport to a more profitable destination. For some time, I made quite a bit of money purchasing selenium where it can be made and transporting it to worlds where it could not be produced.
That is all for today. Going to head to my Dad's and watch the Superbowl. Not particularly vested in either team, I am a Bengals fan, but I would rather see the Falcons win.
cya tomorrow!