Yes, your issue confused me too. A few days ago I bought about USD $16K AAPL and as I had no USD 0 balance, I transferred from my AUD to USD so that I don't have to pay interest on the USD part (Even with a non-margin a/c, they will allow you to have negative USD balance, so long as your overall balance meets the AUD 500 minimum balance). I sold my AUD at market and got 0.79805 to the USD with a commission of AUD2.40. The 0.79805 rate was little different to the spot rate that Yahoo was fluctuating about at the time that one would have had no reason to complain.