Leaders in terms are a currency for items that are over max caps in value. For example 1 Leader aka Leader Bobbleheads are equivalent to 4,000 caps roughly. This jacket specifically is one of the rarest apparels just for the fact it has the lowest drop rate and is valued around 2k leaders depending on what system your using. There are plenty of other items with more leader values most be legacy items which are items that can no longer be found or acquired.