The Gold Chain for this Item Sells for 220k on Hades, the Shell is 5k, but I can confirm this items is worth a total of 5500 GP with a NQ being worth 1750 GP's Hope this helps!
They are useful for monks who want to use counterstance. If they have the negative evasion, theyll get hit better, and therefor can counterattack. also useful for not dodging attacks and counterattacking like normal. im not a monk so i could be wrong, but thats wat i would use em for =P