It'll take 1.8 million gil to get Triple Overdrive onto a weapon, but frankly, you really don't need this ability for characters like Lulu. It's best on Tidus, Wakka, and Rikku.. It drops Triple AP on weapons and can drop weapons with up to 3 slots, so as soon as you get one with Triple AP + 2 empty you can make a Triple AP/Triple Overdrive/Overdrive->AP weapon quite easily.
A page with information about the Auto-Ability Triple Overdrive from the game Final Fantasy X (FFX, FF 10). Read on for more information about the ability including its effect, and its customization requirement.. A guide to quick leveling in Final Fantasy X using the Don Tonberry trick, the fastest method for gaining AP and advancing through the Sphere Grid.