Containers are items used by the two Crafting Skills Apothecary and Talisman Making.
There are four types of containers, one used in Talisman Making and three in Apothecary. They are Talisman Containers, Potion Containers or Vials, Gold Essence Containers and Dye Containers or Mortar and Pestle. There are some differences in the obtaining of these. Talisman Containers, Gold Essence Containers and Dye Containers (Mortar and Pestle) are all obtained from Merchants and so far there are no signs of there being any other versions of these obtainable from elsewhere. But they do have a skill level requirement of 1 so it is possible that once with high skill requirement that gives better results can be obtained later in the game.
The Potion Containers, or Vials, have multiple ways of being obtained. Through Merchants, Scavenging, Corpse drops and (most commonly for the higher skill ones) Public Quest Rewards. Because Potion making makes up such a big part of the Apothecary crafting skill there is required to be a large number or both easy accessible and rare Vials, giving the players the means to focus on either improving their crafting skill with making many potions with easy accessible Vials with low skill requirement, or making strong and effective potions for use in combat or trade with the rare Vials.
Why only one Container for Dyes and Gold Essences Edit
For the Apothecary it is likely that because Dye making and Gold Essence crafting is such a minor part of their crafting profession, it is not meant to be more then a way to make money or customize your character with the Dyes and providing for the Talisman Making with the Gold Essences. And it is therefore likely there are only one container for each of them available because the quality of the Gold Essence is all ready controlled by that of the Gold Dust and the Goldweed, and for the Dyes there is no need to be able to control the quality, the colour of the Dye is determined by the Pigment.