You do realize the cap is 9,999,999 right? You're suggesting five times the literal cap of Gil for ONE TWELFTH of a limit break? That is absolutely ridiculous to even think of if that is the case. Let me know when you find the time to farm for 600 million Gil to MLB something. On the off-chance you're suggesting 50 million for all 12 power stones, then 2.4 million each is more reasonable. However you have to think of the entire picture, not just "this should be more expensive because it's X item" in the small picture.

1 million Gil is quite an acceptable price in the grand scheme of things. Farming golden cactaurs for 1 million Gil and you're still looking at 1-2 hours depending on support items used. So considering that, for 1/3rd of a limit break, you are looking at roughly 4-8 hours of grinding cactaurs. 50 million is not a reasonable cost given the time investment. You might have time, but not everyone else does.