As someone who has collected since 1985 I have seen everything the card industry has had thrown at it. I have seen my 1985 Topps Mark McGwire USA Rookie Card go from $15.00 in 1992, to $350.00 in 1998, and now you can pick it up on ebay for about $10. I have a 1998 Beckett that prices a Ken Griffey Game Used Jersey Card at $750, and today I see it buy now on ebay for $40.
So what is my point you maybe asking? It amazes me the people who tell me they have a shoeboxs of their kids collected 20 years ago, and how they think it is worth a ton of money. I then open of the boxes and see stacks of 1991 green and blue Donruss cards, and 1990 Topps cards. Next comes the bad news, realistically you may be able to sell the box for $5. Most of the time I get looks like I am the crazy one, or I am trying to rip them off. I even had one person who had a 1994 Beckett in hand telling me that one of those cards were worth $50! I try to explain yes, it WAS worth $50, but in today's market collecting is a totally different ballgame. With the invent of the internet, and ebay alone has caused almost any card to be bought at any time of day. In 1994 you couldn't go online to buy a Frank Thomas card at any time, you had to work to find it! A collector could go shop to shop looking for one card to complete a set, thus the supply and demand was much greater. Once the internet came about and people all over the country (and world) were all trying to sell that same Frank Thomas card in the thousands it took the value down from $50 to about $1. Does it mean that card is totally worthless? NO To a card shop in business of making a profit, a $1 card isn't going to pay the bills, but to a collector of Frank Thomas price isn't the issue.
MISCONCEPTIONS: One HUGE misconception in the hobby is the BOOK price of a card. Nobody likes paying sticker price for a car right? The same is with baseball cards! Beckett is in business to supply a value to ensure people that what they are buying has value. But try to take a card with a book value of $100 to a hobby shop and demand $100, after they are done laughing at you they will look on ebay and see that card selling for $10 and if you are lucky they may offer $5 cash or $10 in trade. Hobby shops may mark all their inventory at book value, but don't be afraid to do a little research of your own before going in, don't be afraid to make a friendly offer. Just don't offend them, don't tell them you seen this card on ebay for this much, you need to remember they have bills and overhead too! Nothing makes a hobby owner madder than you comparing costs to ebay prices, so DON'T do it!
FUTURE VALUES: If a 1991 card set is worth $10 now in 2012, I would expect that same set to still be worth nearly $10 in 2030 too. If you are an average collector, unless you pull a 1/1 Babe Ruth Autograph (or a similar card), you should to expect to put more money into your collection then what you could get out of it selling it someday. Today a 2011 Bryce Harper Autograph is going on ebay for $300, but in 5 years if he is a bust that card could be $8. If he is the next Albert Pujols, it could be $1,000. It is a total gamble, like a lottery.
IF I BUY...An example lets say you spend $300 on blaster boxes at Target for some reason, you get 3 semi star game used relics and two minor league autographs and turn around and take it to a hobby store, don't be surprised if they only offer you $50 (if you are lucky). It is just the nature of the beast of collecting!
PRE 1970s: Cards from 1979 and earlier have always had and in the foreseeable future will keep their value. Most of the cards values will no longer have much more rise in values, the only values that will raise in values are higher graded cards. For example if a Mantle card is good condition valued at $400 in Beckett, and you just happen to find an almost perfect same Mantle card and send it to get graded and it comes back 9.5 it could now be valued over $1,000. If you take a 1991 common card valued 10 cents and have it graded as a 10, it still may only be 10 cents (and you are out the $10 grading cost).
Any questions about values or any other questions please feel free to email me firstname.lastname@example.org