My most frequent question sent to me through my vintage cards website is also the question I least like to answer: How much is my card worth? At first, I tried to be really polite in my response about why I really can't be the one to arbitrarily assign a dollar value to somebody's cards. There's too much to consider (condition, etc.), and usually, I don't have enough information in an email to reach a definitive value. However, as time went on, my replies to these questions grew shorter, and I have made a point of sometimes refusing to answer questions about value.
My reason is simple: A card's value is based on several factors, including its condition; ultimately, if you try to sell it, your card will only go for whatever somebody is willing to pay for it.
For example, let's say you have a 1955 Topps card of "Rip" Repulski (#55). He's a common player, so he's grouped with the rest of the "commons." Say, for example, High Beckett on this card is $12, low Beckett is $6. But those prices are for a card in Near Mint condition; your card is maybe in Excellent condition. So realistically, when adjusted for condition the card price is somewhere around $4. Then, try to sell it to a card dealer...if he even bothers to take it, he may give you a $1 in-store credit or 75 cents. If you put it up on eBay, most bidders won't touch it at $3 unless they really need the card. And even then, you're out whatever final fees eBay and PayPal take.
Result: a card that is listed at $12, that may fetch anywhere between $1 and $4. And you would be upset if I told you your card was worth $12 if you ended up selling it for $2. That's why I don't mess around with card prices.
Happy New Year! - I decided that New Year's Day was the perfect time to feature the first card of the 1973 Topps set. That was back in 2011, and today is the first day since...
2 months ago