The answer is … a lot of things. 8000 won (roughly 8 bucks) can buy you 8 bottles of soju, a cocktail at a club in gangnam, or a used novel at What the Book?
It took me a while to learn, but fruits and veggies are cheaper the further you get from the supermarkets. Buying from the back of a truck, or an adjumma on the side of the street is the way to go. Recently I bought 12 kiwis and 10 bell peppers (capsicums to the Kiwis) for 2 dollars each.
But this haul is one of my best ever. 5 onions, two ginormous peppers, a head of lettuce, 4 kiwis, a mondo bag of garlic, and 2 carrots all for under 8 bucks. Perhaps it’s not Central America/SE Asia cheap, but for a huge city, it’s rather pleasing.