I believe it is because of bid and ask spread.
GJ have 7-8pips spread. EU have lowest spread which is 0.5pips. Quote for oanda platform.

Or maybe because of interest charged on open trade?
If you short high rate currency against low rate currency, you need to pay interest every seconds for oanda case.
It is called swap rates: http://www.ibfx.com/tools/swaprates.aspx

Isn't that what we called spread?

One thing you should make a habit is to see the spread before even entering.

Swap rates are only applicable if you leave your order overnight. Overnight means 5am Malaysian time. You will be given interest for buy orders and charged interest for sell orders. Swap rate is not charged at per second rates.

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Added on August 18, 2009, 11:30 am
That depends on the broker that you use. The broker that I use has controlled spreads and the EURUSD pair is controlled at 1-2 pips with the GPBUSD at 3-4 pips. The spread does not move much as they control it. Some brokers will raise their spread to 20-30 pips, which will eat into your profit.

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Added on August 18, 2009, 11:36 am
You got it the other way around. High spreads happen during peak activities so that the broker can earn more. It also happens during news breaks that would affect the market. If you are a broker, you would encourage more trading during low volume by reducing the spread, not increasing it. When breakout news happens, people will trade and that is the time to increase the spread to earn more for the broker. Do keep in mind that they broker only earns from the spread they charge you since they don't charge commissions for retail traders like us.

I would like to make a correction on your part. Swap rates for mt4 brokers are calculated by days... on oanda.. its calculted by the seconds.. every second counts for the payment/receiving IR..

Oanda?? if i am not mistaken the beginning cpital should be 5000usd
for the beginner like me use FXCM.....

danny,since ur on demo..u can try put a sell order ( limit order ) on eu @ 1.4400...