I would disagree a little there, Jorgen. Many Earth nations have developed well despite not being self-sufficient. Just to give three examples of high-tech & rich countries that absolutely could not feed their existing populations without food imports: Finland, the UK and Japan. Similarly, very few countries are truly self-sufficient when it comes to natural resources - we don't even have to go for rare earth minerals as even more mundane minerals cannot be found everywhere and have been traded for centuries. Sure, many countries have implemented methods (tariffs/subsidies) to protect their domestic food production to maintain some local capability but it's not like it's enough to feed the population, it's more to placate local populace.
Similarly, I disagree with Migi that low-value bulk goods would be transported through space. Of course, in the real world that makes no sense because the cost of KG from Earth surface to orbit is exorbitant and will probably be prohibitive for that sort of trading for decades if not centuries to come. But just like 17th century galleons couldn't transport low-value bulk goods in numbers enough and fast enough to make it economical, modern bulk carriers can and do. And in Aurora, the miracle of TN-tech means that launch costs and transportation costs are negligible, to a large extent.
Combined, this means that in Aurora economy, it very well might be entirely feasible for certain planets to export gigantic amounts of food stuff - not just rare delicacies - to other planets where food production is more difficult/expensive. Just like the current trade goods seem to include low-value bulk goods. But adding food currently is not beneficial on its own, it should be part of a larger economic overhaul of the system. Maybe for version 3.0!
I don't think I meant that every little country is in any way 100% self sufficient in every category that is obviously not possible depending on where that country is, especially in natural resources. In many cases you have to view societies in areas or regions rather than countries. A small country with only a million people for example can't possibly have a viable industry in every sector, trade is therefore very important, food today is just one industry among many.
What is meant is that any society will try to be as self sufficient in every area of industry as possible as this enhances the industrial versatility, innovation and wealth of the nation as a whole. In some cases you have to look not at just countries but at regions or collective economical areas.
When it comes to food there is also a very large difference between bare minimum for a society to survive and the wealth of luxury food that we consume, especially in wealthy nations. When we talk about entire planets resources and needs you would need to secure enough basic goods for survival, relying on imported base goods is very dangerous, that is why having a larger trade deficit in certain areas can be very dangerous, especially food. It is one thing to trade in order to secure variety another to be completely reliant on it, which happens and also objectively had serious consequences in history, ancient Rome is a good example.
Also... when you look at food trade for example allot of it is food that we don't need, luxury products, things that can be replaced by more basic products if really needed. We can all drink just water instead of Coca Cola for example.
Countries that have over time been successful and developed their economy have generally been those with a high degree of dynamic industry, not the ones that relied on producing one thing or rely on natural resources only, that generally only produce inequality and wealth for a few and not the society as a whole. You need to spread the wealth in order to have real sustainable growth and productivity in a society.
It obviously does not mean that most societies have above average proficiency in some areas and less in other, that is just natural. But trade will not only be for natural resources but also to distribute a wealth of choice. No one like to buy just one and the same pair of clothes, car or food, you want variety.