Very simple (i would rather use example without introduction).
Combat armor cost = X metal parts, Y alloys, Z leathers
Brotherhood amor cost = 3X metalparts, 3Y alloys, 3Z leathers
So simply, the difference of quality between finest stuff and "almost finest stuff" could be small, the difference of needed resources could be big.
It would cause, that players, who want to join specific situation (PvP, PvE,..) could do that without many hours per day gathering, but also players, who have more time could be "rewarded" for their effort. Also this finest stuff would be better trophy in PvP than basic one.
Problems, questions, solutions..:
1) Not every PvP stuff have its own "almost finest" clone (I.e.: there is not alternative for Sniper rifle, and sorry, scoped hunting is not).
2) People could think that difference is not worthy.. but you know .. if you collect tier finest stuff (weapon, armor, ammo, drugs?,..) and put it on at one time, it would give you advantage.