In some instances they could [as could additional fuel burn from takeoff and airport landing costs] but airlines have done the maths. Flying hours also count towards mandatory overhauls and part replacement/retirement, and in the case where the airframe is due to hit its hours limit first, the extra takeoff cycles aren't going to make any difference.

Fuel burn is also usually the largest component of expenditure, and is especially likely to be when looking at elderly freighters with low capital costs and relatively inefficient engines