On the difference between exchange value and use value. /
The use value is the potential usability of a thing. It can vary between individuals and depends on the user. Thus, the use value of a cigarette for a smoker and a non smoker is very different. /
The exchange value is the equivalent of the price on the market. If the total exchange value of a thing collapses, such as of a city, its land and houses, although it has no value on the market, there nevertheless remains its use value.