Nocks is not a store that hangs a pricetag on a product at a price they see fit.
It's an exchange where the price is determined by supply and demand. 
See https://www.nocks.com/trade/NLG-EUR

Now as an extra service you can buy Gulden at Nocks using iDeal or Bancontact but that's a frontend where you actually do a marketbuy on the exchange.