I believe the cargo issue comes into play when considering the B777.

On the MAN-DXB route, the passenger numbers couldn't justify 2xB77W's at first, but the extra cargo capacity made it worth it.

The passenger loads have increased to the point where they are considering a 3rd daily.

The demand has pushed the lowest price of a MAN-DXB return to well over £500!

Cheers,
Rick