I was WAY off...post 1980 cards are sought after!

[Tripredacus]

Cards from early to mid 2000s have a higher value due to the fact that there were so many product options at the time. This meant that a shop would be buying more variety. This resulted in perhaps only 1 box being available in any area, or some sets not ever showing up. There are still sets from the 2000s (and even late 90s where this problem began) that I've never seen cards of, or sets that I have seen or own cards of but have never seen boxes. This was also the time when retail exclusives had showed up on the scene, either whole releases or variant releases that would only be at department stores.

The result ended up that inserts for set from those years can be worth quite a bit. Some inserts or parallels are rare enough that they do not show up on ebay often.

Take this example. There is no listing on Ebay in active or sold for a box of 2003 Upper Deck 40 Man.