The per pip value of the EURAUD on the otherhand changes as the price changes so if you were to open two trades at different prices, the pip value would be different between these two trades.
The USD pip value change for EUR/AUD does not matter because it is always compensated by AUD/USD rate changes. Going long EUR/USD and short EUR/AUD is the same as opening an AUD/USD position (the size depends on the rates at the time of entry). That's a mathematical fact. Until you understand, you will get confused by these sorts of locked trades.
somehow this exposure and pip value being different for EURAUD from Trade Open to Trade Close
No, the exposure of the EUR/AUD short trade does not change from the moment of trade entry to its close. What changes is its pip value, which depends on AUD/USD.
I don't know exactly what is happening,
But I do, and I have explained it in one of the first posts here.
Maybe someone can expand on this a bit or provide a contrary opinion as to why the system is profitable.
The system was profitable because it managed to open AUD/USD trades profitably enough to compensate for the additional spread/swap losses. Had it used normal AUD/USD positions, it would have been even more profitable.
I know you (Enivid) said that this was just basically trading AUDUSD in the opposite direction at a certain lot size, but that doesn't quite hold water in all cases.
Actually, it does - as I have shown in this thread twice already and since no proof of opposite has been presented.
Look at the trade that opened on September 9th (See attached that I took a screenshot of). Using your idea with the AUDUSD, then this basket should be an equivalent of I believe about 0.145 lots as a Long Position (correct me if I am wrong). The Overall Gain shown by all 3 pairs here is $76.08, but if you then would calculate the profit of AUDUSD with a rough 2 pip spread at 0.145 lots, I come up with almost double at a gain of $138.33 when I would expect closer to the $76. Can someone explain that?
I could not find any September 9 trades on the screenshot, so I provide calculations on the September 21 trades instead:
Short 0.43 lots of EUR/USD @ 1.11543 = selling 43,000 EUR for 47,963.49 USD.
Long 0.43 lots of EUR/AUD @ 1.47192 = selling 43,000 EUR for 63,292.56 AUD.
At this point, you do not have any EUR exposure. What you have is long exposure to USD (47,963.49) and short exposure to AUD (63,292.56), which is a short AUD/USD position of 0.6329256 lots with an open price of 0.75781 (47963.49 / 63292.56).
Now, you add a Long 0.43 lots of AUD/USD @ 0.75792 to it.
This effectively hedges 0.43 lots part of the Short AUD/USD position (locking 1.1 pips of loss, by the way).
The remaining unhedged part of the short AUD/USD = 0.6329256 - 0.43 = 0.2029256 lots.
Now, however EUR/USD and EUR/AUD move, the profit/loss depends only on the move of AUD/USD. Your EUR exposure is completely eliminated by your EUR/USD and EUR/AUD hedge.
At the Close time, the AUD/USD Bid rate was 0.75223. Let's assume that Ask was at 0.75243 (2 pips spread). The resulting profit should have been:
(0.75781 - 0.75223) x 0.2029256 lots = $113.23
With 1.1 pip loss locked in a hedge, you have to subtract $4.73 from it. So, it's $108.5.
The actual cumulative profit of the trades was: $542.66 - $244.67 - $192.13 = $105.86.
The difference is attributed to paying two additional spreads for unwinding this 3-side hedge - the spread on EUR/USD and the spread on EUR/AUD.
By the way, the calculations above are valid only if you enter and exit the trades at the same (or nearly the same) time. Myfxbook does not list seconds for time, so I cannot check if this is actually a case.