Why are old comics valuable?

Like all collectibles, the value is determined by the number of people who think they need it and the number available for sale. Investing in collectibles is sometimes refered to as the "greater fool" principle - a fool will buy something with no intrinsic value hoping a bigger fool will come along and offer more. Another basic reason that Golden Age (World War II era) comics are valuable is because of the very low number of the comics that were originally printed then. This fact, coupled with rationing efforts that required people to recycle paper (among many other things) for the war effort and the rarity of surviving issues due to the lower quality paper used in printing create a limited supply to meet a very high demand.