@minus: While I agree that “all costs” must always be used carefully and is hardly ever right I think you should also consider the following things:
1. Cairo underlines one NO of Italy even if Gibraltar might fall into the hands of US/UK for 5 IPC each turn
2. You must consider that saving units cannot win the game once the income somehow gets imbalance and time will clearly play into the axis’s hands
So it clearly depends on if even w/o Cairo the allies have realistic chances to win even in the longer term. If time will only play for axis in case Cairo falls, I can imagine there are situation where you should either stand or resign.