Could we look at Lux E mana costs?

These doesn't seem excessively high? 70 / 85 / 100 / 115 / 130?

To compare...

Ahri's MAX Q costs 85 mana

Galios MAX Q costs 80 mana

Xeraths spells cost less at all ranks and he has a mana returning mechanic

Anivia's Q costs less at all ranks and almost always build mana items

Zigg's spells costs less at all ranks

There's no reason I can see as to why Lux's E has such a high cost considering there are other spells that give the same effects (aoe slow / zoning / etc ) and cost less / lower CD. Is there something I'm missing?

If you don't want to drop the mana costs could you at least look at adding some sort of mana returning mechanic when she attacks champions and / or minions marked with illumination?