That is factually totally incorrect and I have provided the math on this site down to the penny. And you don't understand how IB charges for interest rates. It marks down credit interest and marks up debit interest. It's really not that hard mate. Take a look at the plenty examples on their website.
Did you supply the math right to the penny that trading fx futures is equal to trading cash fx while holding overnight with IB ? Where did you accomplish that feat ? Please don't be shy, do it again on this thread, we could do with another of your arithmetical nonsense before dinner.
I never said it includes holdings with rolling. Read more carefully. I chose every single word carefully in my claim.
So Oanda's interest rate spread on majors seems to be 0.4% (yearly I suppose), what is it at IB? 0.4% is very reasonable imo, assuming you are not into complex arbitrage spreads, but just outright, since 0.4% is just a tiny bit compared to what you are going to win or lose on the difference in buy / sell rates.
From what I understand with IB on long EURUSD it comes to 0.5% to 1.64% and short eurusd 1.5 to 0.5%, depending on the position size. As there is no interest paid on positive balance on eur nor usd you can chek the table below on what is charged on the negative balance: https://www.interactivebrokers.com/en/index.php?f=interest&p=schedule2
be patient, don't complain, you'll get there someday if you keep your losses short and let your profits ride
don't be so touchy. mate in informal british english means friend. at least he didn't call you a whore monger but give it time.