That's about the ABV of Rum so that's not too bad, especially for that price. I've never had Soju before and I'm not sure if they have that over here in the states, especially in Tennessee, but it says on Wikipedia that it can range from 18% (like you said) up to around 50%. I don't know if they sell the higher proof stuff commonly over there but if I ever make my way to Korea I know exactly what I'm buying.