The formula for the increased MP cost is as follows:
Damage increase is only applied to spells that use the physical, magical, and cure formulas; spells that use a different damage formula, like Demi, are unaffected, but still suffer from the MP cost increase. Status effect spells' hit rate is boosted by the same formula damage is increased by. Multiple MP Turbo Materia can stack on the same spell up to the maximum of 50% increase, the strength of a single L5 MP Turbo. MP Turbo Materia only affects abilities that the linked Materia can give at its current level.
MP Turbo is found at Whirlwind Maze.
Magic Booster can be customized onto a character's weapon to increase damage or recovery with magic by 50% by the use of twice as much MP as normal. It requires thirty Turbo Ether items to customize. Lulu's Onion Knight Celestial Weapon has the ability naturally when powered up, in tandem with One MP Cost causing most spells to be 2 MP.
The Soul of Thamasa accessory grants the Magic Booster ability, while in the International and HD Remaster versions, the Garment Grids Peerless and Last Resort can grant Magic Booster by passing through a colored gate.
Turbo MP can be learned by White Mages as a Support ability through the White Robe for 300 AP. Turbo MP boosts damage of most abilities, even some that do not require MP usage, and increases Accuracy by 15. However, MP-using spells cost double the MP when Turbo MP is equipped.
Turbo MP returns with the same effect as from the previous game, but because of the new MP system, spells are thus less efficient, as they require twice as many turns to charge up for. This can be alleviated by using a Cannoneer. The ability is learned by the White Mage for 250 AP from the White Robe.