I don't know how much it costs to run a T* but typically the 744 runs to around $40K per hour assuming LLPs and burdened maintenance at around $3K per flt hour
Get the RAF to provide the fuel, markup for risk, and someone could make a nice return from such a venture.
As a matter of interest, has anyone ever tried to cost a RAF Tri* sector against a similarly-laden 767 sector, including maintenance costs etc? Even better...VC10?