It's a familiar situation: someone is cleaning out the attic and finds that old box of baseball cards that was owned by a relative, or perhaps a spouse had been holding on to them for years, insisting they were a prudent investment.
What one person (typically the one who bought or inherited the cards decades earlier) sees as treasure, the other sees as a hoarder's junk. This disagreement may continue until the cards are finally taken into the local sports memorabilia shop for a professional opinion, where most are disappointed to find out the collector has little interest in their wares.
So why are baseball cards often thought of as a valuable collectible investment, when most need to be sold in giant lots just to get a few dollars?
A good start to answering this question is to understand the origination and evolution of baseball cards. In the mid-19th century cards were made by placing a photograph onto cardboard, a niche practice that preceded modern printing technology. Towards the late 19th century cards depicting baseball players were just one type of "trade card", which was a popular form of advertising at the time for many types of businesses and politicians.
During the 1880s cards were mass produced for the first time as advertising enticements for tobacco products and would be included in tins or packs. Near the turn of the century this practice began to fade as the tobacco companies combined into one large corporation, The American Tobacco Company. When the conglomerate was busted by the U.S. government trading cards were once again used between competing companies. The period between 1909-1915 is considered the finest, most desirable era for vintage baseball cards, producing famed pieces such as the T206 Honus Wagner.
As America found its way through World War I and the depression era, tobacco companies became less involved with printing cards while gum and candy companies picked up where they left off. Throughout the 30s and 40s cards were continually produced and by the 1950s the Topps Chewing Gum Company of New York had began to monopolize and modernize the industry, introducing concepts such as the rookie card into mass production.
The growth of Topps and the card industry throughout the 60s and 70s was accompanied by a growth in interest from collectors and hobbyists. By the 80s, it was a full blown craze viewed by many as a viable investment plan, and were considered so valuable that a Major League umpire was even arrested for allegedly shoplifting them. The card companies, however, did not make a habit out of disclosing the amount of cards they produced, and by the late 80s many consumers were investing in a product with constant and virtually unlimited supply.
This era of mass production created a busted bubble, and the value of modern cards have never really recovered. The number of cards in circulation from 1985-1992 is considered especially high, rendering nearly all of these cards virtually worthless.
On the flip side, the vintage cards that ignited the hobby are as valuable as they ever have been. A family recently discovered seven very rare 1911 Ty Cobb cards while going through a deceased great-grandfather's estate, which are conservatively estimated as having a seven figure value. This amazing discovery de-throned the 2012 "Black Swamp Find", where an Ohio family discovered a near complete set of 1910 cards. The collection ended up fetching a bit over a half million dollars at auction.
The odds that most of us will stumble upon a rare or legendary find is naturally low, and even lower that the cards would be in decent enough condition to demand such hefty sums. Still, a simple understanding of the timeline and evolution of cards can give a non-collector some good starting points for understanding the market. Happy hunting!