Ever since Da-Planet opened up we have been asked why we don't differentiate from 1st Edition and Unlimited. The answer is that we kinda do.
We sell a lot of products on eBay and most buyers don't put much of a premium on 1st Edition cards on recent sets. The premium only consistently exists on the older iconic cards. The key work is "consistently" as we will see temporary differentials on newer popular cards but those change with the Meta so we would consider them risky short term investments.
An excellent example of one the iconic cards is Dark Magician Girl MFC-000 .
The 1st Edition is around $40.00 on the online stores BUT sells for over $45.00 on eBay.
Other examples of some of the iconic cards are:
So as you go search through peoples binders look for the icon 1st Edition cards and don't be afraid to pick up the cards in played conditions because they still can be sold on eBay for a decent price. You can use your profits to trade up and who knows you may find that MINT 1st Edition Exodia Head or Dark Magician Girl one day. Those will retain their value possibly increase over time. If you are lucky and the card becomes part of the current Meta then you will see a significant increase in value as the tournament players that want a bling deck will drive the price up.
Very interesting, goes to show there's a big difference between playability and collectibility. New cards gain their price tag because of their tournament status, but if Konami ever stopped supporting organized play, it's these iconic collectibles that would retain their value as collectibles.