I'm talking about Yugoslavia and 80s. Borders were officially quite tight (you couldn't import anything beyond some small value), but lots and lots of people used illegally traded foreign currency to buy food, clothes, toys, computers(yes, you could not buy zx spectrum in Yugoslavia), etc. and bring it illegally over the border.

It is likely that things were different in 70s and even before that, because rules relaxed a bit in the 80s.