That sounds way off. Way less than 25% of tax revenues go towards the military (more like 2% in Europe). Then the bombing campaign must be a fraction of that.
Income tax total for France was 57B euros. The employer (payroll) tax isn't counted in there. Nor are some of the other social charges. It's a progressive tax designed to keep low-earning households from paying much, if any, income tax.
French ministry of defense is 32b€. You can't move an aircraft carrier without submarines and destroyers, you can't move a fleet without the satellites, you can't do anything without headquarters. We are currently active in 2 wars and present in a lot more places, but without wars, there'd be no need of a big headquartets; so how would you, yourself, make a honest pro rata of the cost of each war?