In most games, people will try to find how damage calculation works and come up with a formula, so the effective HP can be known and compare build with every gear upgrade and calculate the cost, but in BDO there is no floating number when we hit or get hit that shows how much damage is dealt/received, so there is no data to be gathered for doing calculations. In the end it's like buying a cat in a bag. I was using heve set (helm/gloves/shoes) with 221 DP and 2800 HP, then i "upgrade" to boss gears DUO giath/muskan/bheg. 238 DP and 2600 HP (costed me around $80 for the Artisans). But it's not that much difference, and seems like I bought more accuracy and a few evasion for $80. The damage reduction isn't that much different between heve and boss gear. There's also hidden stats in gears, seems like the devs are really trying to hide the damage formula.