Doesn't seem worth it for just +3 evasion... Not sure if I'd fork out the cash.
The charges last 30 minutes as long as you keep this piece equipped and don't zone or die. That's 25hrs worth of charges, which is more time than most need to get to a better body piece.
Overall though, the body piece is fantastic if you can either craft it or if the price would come down. They rarely sell due to the stigma most enchanted weapons have; however, the current profit margin is high enough that it would be pretty easy to lower it and still be fine.
Some people will fork over the gil for that extra edge. For some endgame items, how many hundreds of thousands of gil extra do people pay for just one more point in something?