Each Suite of the minor arcana is associated with one of the four classic elements. Cups - water. Swords - air. Wands - earth. Coins - fire.
Coincidentally, "yang", like fire, is also associated with wealth, like coins, in Chinese Astrology and Feng Shui. Cups in tarot are usually shown as golden or metallic goblets. Metal is a supportive or generative element for water in the eastern tradition as well.