Axes have more and more become viable alternatives to swords, but still loose 2 durability when attacking an entity. That means that using an axe as your primary melee weapon costs 3 times the resources.
(2x when using and 1.5x when crafting/repairing, as they require 3 ingots/diamonds instead of 2)

This had been discussed in MC 1.4.7 (MC-9479) and was resolved as WAI, because "axes happen to do more damage, but aren't intended as weapons".
Now, axes can be enchanted with Sharpness, Smite and Bane o.A. and even have a special attack to stun shields, so they are definitely inteded as weapons by now. The double durability loss however diminishes their practicality in survival.
Therefore I suggest to revisit this issue, I hope the changes in the last 3,5 years make you reconsider.