Material wise you need 20 iL of materials to create them (i gave you that one for free though with your Profession, as there are a few other things needed for creating this special Elixir). Also Dl to create one is 30 (so with your high score in Herb Craft you would need a 13 on the die roll). 

Cost wise... you could probably sell something like that for 30 iL cause they are somewhat amazing things. The Lunar Blossom Elixir (as it is sometimes called, another aptly given name being Celestial Healing Elixir. your character knows that the reason for them being called Lunar Blossoms is because it is best to harvest them and either use or preserve them on nights when any of the moons are full or during days when the Day Moon is full)