Focus Mana Cost Efficiency INCREASES mana cost when equipped (reproducible)

Steps to Reproduce:
Log into character IceeyQueen (league: Abyssal).
Go to hideout.
Unequip both foci.
Check skill tooltips for Frost Bolt and Arc:
 • Frost Bolt shows 105 mana cost
 • Arc shows 110 mana cost
Equip focus Rapture Anthem (20% Mana Cost Efficiency).
Check skill mana costs again:
 • Frost Bolt increases to 126
 • Arc increases to 131
Equip second focus Skull Chant (also 20% Mana Cost Efficiency).
Check skill mana costs again:
 • Frost Bolt increases to 125
 • Arc increases to 130
Note that both foci increase the mana cost instead of reducing it, and they do so by slightly different amounts even though the stat is identical.

Observed Result:
Equipping either focus causes higher mana costs on skills that should become cheaper.
The two foci produce different mana costs despite having the same “20% Mana Cost Efficiency” modifier.
Behavior is consistent and reproducible.

Expected Result:
Mana Cost Efficiency should reduce the displayed mana cost of skills.
Two items with identical Mana Cost Efficiency should produce identical mana cost values on the same skills.

Extra Notes:
Tested in hideout with no buffs.
Issue affects multiple levelled spells (not just Frost Bolt / Arc).
Appears to be consistent across both foci.

Both Foci have +3 spell levels on them, so apparently not a bug after all. However, the inconsistency in mana costs remains an oddity.

I went back and checked, the foci had 21 and 23% mana efficiency, oops. Sorry.