Besides the stats you see, some gear have a chance to add something, like a damage multiplyer (or many other types of bonus) - that is referred to a proc

The proc is driven by rng (“random number generator”) same as a dice roll- roll a 1 you get the bonus
There are different reasons the gear may have the chance to proc, such as ”do damage”, or “take damage”

The proc is written in the gears description, usually u have to scroll down

Gears have differing chances of proc which makes some gear/sets more desirable
Krak is easy to proc most gear, also some procs are massive & stack with other procs
Also, procs have a “cool down” which is a set time that has to pass before the gear has the chance to proc again

Many use krak gear to proc & switch to that better stat zaar set to improve output
So yeah krak can have worse stats but what it does justifies that crazy price difference

Maybe I missed something, lemme know if that’s not clear