Solution
92%.
If anyone was here to witness such a feat, shock would be the least exaggerated reaction that they could give. To do this on one's first try was unheard of, so much so that maybe in the history of alchemy, it had never happened before.
If this Common Grade pill appeared in the market, there would be countless clans with toddlers on the rise that would fight tooth and nail to make certain that it was their son or daughter that got the chance to consume it. This would be the case even within the Seventh Heaven, maybe even the Eighth. The value of this pill was that exaggerated.
Of course, value was still a relative term. They would pay an exorbitant amount in comparison to the worth of a Common Grade item. However, it would still be greatly lacking in comparison to an Earth Grade treasure, for example. Though it might dwarf many Black Grade pills of far lesser quality.