There could be several reasons for this, firstly, where did you buy your Bitcoins from? From a local trader, exchange site, or BTC bank? Some places charge a higher amount than what it is to earn profit, which you may have bought at a higher price.
Next, the price of Bitcoin may have dropped in the few hours that you check, so make sure you keep a record of the cost and date+time of when you bought it. It is always a good habit to keep a portfolio or logbook of your transactions so that you can refer back in the future.
