Lightstruck beer is beer that has been exposed to ultraviolet and visible light. The light causes riboflavin to react with and breakdown isohumulones, a molecule that contributes to the bitterness of the beer and is derived from the hops. The resulting molecule, 3-methylbut-2-ene-1-thiol, is very similar to a skunk's natural defenses. 125 bucks, or in other words, the price of three bottles of Carlsberg or Budweiser for the molecule of Skunks fart? Eeeew!