Modern Carbon brakes are much more efficient than the old sintered metal brake units. They operate best when they are hot, but most importantly the brake ware is also reduced when the brakes are hot. The resins that bind the carbon is baked 'on the wheel' so that when the brakes are cold they ware much quicker. Easyjet are correct to use this method as it allows the brakes to heat quickly after touchdown. The price of a carbon brake pack is very cost effective for the time the unit is on the wheel and the applications used, if they are operated properly. I don't know what easyjet do but many operators now lease the brake units and pay a fix cost depending on the way they operate. Easyjet might pay a sum dependent on the use of Autobrake level 3, for example.
However, the biggest saving of all comes from FOD (Foreign Object Damage). The cost of engine damage is now far greater than using the brakes. Full reverse should never be used unless it is absolutely necessary as the chance of ingestion of foreign matter into the engines is hugely increased with reverse thrust.