It still saves you a bunch of money....key is repairing with dark matter when your gear is around 10-15% durability (ok, never run a DF or roulette with gear that low in case you wipe several times).
12-13 slots for 80g = 960-1040g
Repairing 12-13 lv50 armor around 10-15% durability at the NPC is over 2500-3000g
