An excellent point that entirely slipped my mind (blame the post iftar gin and tonic....)
EK have stacks of through traffic (I'll confess I don't know the split, but I would bet most of EK's traffic is non-terminating at DXB), a charter will have none. That again offsets costs of the trip. Another point against a charter.
As an aside... Non network long haul carriers have a hard time in DXB. Remember SilverJet? No connecting traffic...
TA