Quoting Boeing Aero:
the numerator of the ci is often called time-related direct operating cost (minus the cost of fuel). items such as flight crew wages can have an hourly cost associated with them, or they may be a fixed cost and have no variation with flying time. engines, aux- iliary power units, and airplanes can be leased by the hour or owned, and maintenance costs can be accounted for on airplanes by the hour, by the calen- dar, or by cycles. as a result, each of these items may have a direct hourly cost or a fixed cost over a calen- dar period with limited or no correlation to flying time.
in the case of high direct time costs, the airline may choose to use a larger ci to minimize time and thus cost. in the case where most costs are fixed, the ci is potentially very low because the airline is primarily trying to minimize fuel cost. pilots can easily understand minimizing fuel consumption, but it is more difficult to understand minimizing cost when something other than fuel dominates.
Interesting to see the real reason behind EK's choice.