In my setting there's a planetary system that did something bad and the rest of systems put it under embargo that lasts for more then a half century.
In order to simplify things how would country be affected on economic level if it was an island like Cuba, but placed somewhere far like Tahiti, and without any friends (unlike USSR for Cuba), the most similar things today is probably North Korea?
The international fleet can't stop every smuggler, but no large ships could enter or exit.
The country doesn't have any extremely valuable resource like oil or diamonds that would tempt others to cheat
The international community has no ability to overthrow the government or invade it.
The country doesn't want to change in order to be accepted back.
The country has relatively free market economy
After reading about sanctions in history below are my expectations :
Lot of the products will be unavailable since they can't be produced economically or even at all, due to economy not being able to acquire inputs, knowledge or economy of scales. Wanna chocolate, sorry pal we can't get grow any cocoa here.
Small & expensive products will be smuggled. Watches, processors & many drugs are small in bulk and if there is large price differential smugglers would be tempted. I don't know what they would pay with though, precious metals if they have them, selling family jewelry.
Bulky products that are necessary for the economy would be produced locally and they would be poor man's substitutes with a twist of being relatively expensive. In order to serve farmers , a factory would be forced to simplify their design to use what is available locally. I'm sure that engineers will think of some very simple machine designs (tractor, truck or car) that does it's job and it's affordable enough that locals could buy it. If they show up with the same thing on the global market they would be laughed off.
Only the products that economy has a comparative advantage would be very cheap. If they have a excellent climate for growing tropical fruits and can't export them, prices would be cheap.
They would be forced to (poorly) maintain lot's of the technology that can't be replaced for very long time.
In short even with magic of free market working, I expect them to be poor and backward.