$4 is an absurd price for this DLC considering the chests and loot are already in the game and all it adds is the maps that show how to find it. The maps were very straight forward and pretty easy to find, took me maybe 20 minutes when you cut out the travel time in between points. $4 for a 20 min scavenger hunt is just an incredibly steep price.
The armor itself does look really nice and is useful to avoid repair costs as it all repairs for a 10th of a groschen regardless of condition, but that isn't the reason to get this as you can just look up the locations on a wiki for it. So buying purely for the adventure aspect of using the treasure maps, it's a hard no unless you can get it for a dollar or less on sale.