"벌" is a noun counter, normally applied to units of clothing (like a suit). Here, a loose translation of the passage :
"Of course, it is now out of fashion, but because it is so cheap, with the same amount of money for the (previous) price of a single, new unit, you can (now) buy multiple units."
In the above sentence, "벌" refers to the "unit(s)". There are various counters that are more or less shared by Chinese, Korean, and Japanese. They are sometimes based on various categories of objects (books, sheets of paper, etc.), but sometimes they are based on the shape of the objects.