I have been wondering when I hear on pawn stars “this item is very collectible”. What makes an item collectible? People will collect almost anything.
Things are generally considered collectible due to scarcity/demand, but in that context, It usually means that that particular specimen is in exceptionally good condition.
Collectible or valuable and marketable? Those are two different concepts that don’t even overlap that much. Collectible items just need to have a significant number of people that are interested in collecting a set. It could be Beanie Babies, Star Wars figurines, stamps, coins, baseball cards, comic books, cars or motorcycles etc.
Being “collectible” alone doesn’t mean much in monetary terms. Most items decrease in value over time no matter how you arrange them into sets and fads are more the rule than the exception.
However, there is a subset of the collectibles market that is valuable and it almost always depends on two factors: rarity and condition. That could mean an extremely rare Honus baseball card, an unusual Indian motorcycle or an extremely rare coin in good condition. The problem is that you cannot predict valuable collectibles in advance because, if that was possible, many more people would buy and preserve them paradoxically destroying the value for everyone.
It takes a very rare series of events to produce valuable collectibles. There has to be very few surviving examples, only a few are in good condition or better and there has to be a market of avid enthusiasts for the item that are willing to pay big money to have one of relatively few surviving examples of the item. There is little reason to it except for those broad factors. Lots of things only have a few surviving examples and no one really cares. However, there are still a number of select categories that have passionate collectors communities and organizations with specific “Holy Grails” with market prices to match those finds.
In short, it is just supply and demand but the definition of demand in this case is more nebulous than it is with things like everyday commodities.
It’s an interesting question, “Rarity” by itself of course means little, because plenty of things are rare or even unique and not particularly desirable. So there is no demand. Vintage, “antique” or even ancient isn’t enough either. Plenty of ancient roman coins around - they are old, but not rare. I suppose the question is further whether collectables are particularly valuable or not.
One thing that helps a lot is if the items are “checklistable.” For instance, comic books are good, because you have databases of all issues with issue numbers. (The challenge is to fill in the out-of-sequence special issues, such as issues released only at Comic-Con, or issues with alternative covers.)
Being able to say, “Yes, I would know if I had the entire set” makes collecting easier. It gives you a goal you can work toward.
Stamp Collecting is another hobby where you can work from a checklist. Okay, no, you aren’t gonna find a 1908 Ben Franklin, but since you know it exists, you can reserve a space in your album for it. Collectors tend to be optimists!