help required in buying wireless power bank

i am looking to buy a power bank and liked this idea of not requiring a wire to charge my nexus
also the plus that it can be used as wireless charger
i dont have both so it can fulfill both the needs
any idea how much is should be worth ?

http://www.ebay.in/itm/321861957627?...84.m1555.l2649

hope somebody can help me ..thanks in advance..