I had raised similar concerns regarding another website last year & was given the explanation that it is a marketing ploy to attract more customers & have the prices look more attractive. At my trading platform, I charge a flat 1.5% fee + sevice tax +rs.10(transaction cost). There are no hidden fee or fine prints.
I can see you are comparing two different type of services altogether. What exactly you do as a part of ibitcointrade.com is more or less a escrow service (except that the seller dont know the buyer and you help the buyer/seller to find the counter-party through your web service) where you are not taking any risk and the 1.5% fee you charge adds to direct profits. It is same with bitquick.in as well. These two services are not pegged to any exchange rate from what i know and what ever rate at which the customer is willing to buy or sell is offered to the potential counter party.
I do not complete agree with the reason you have heard last year. What Unocoin does is acting like the real trader. Unocoin will become the buyer if there is a seller and will become the seller if there is a buyer. There are more complications here - will explain when i reply to the OP in next post.