[Discussion] Are pins within Mystery Pin collections distributed equally?

If I purchase a "Mystery Pin Collection" box that contains two random pins from a collection of eight, do I have an equal chance of getting any of the eight pins of the collection? In other words, are the eight pins of the collection released in equal amounts or is there some artificial rarity? (For those of you who speak Magic the Gathering, are some pins of a specific set rares, while others are commons?)