If no one else knows that the card has been opened before it's sold they can't offer a higher price and get the card
Create endless combos to suit your aesthetic
A big card that I noticed was a first edition Blastoise however after doing some research something didnt make sense to me
To give a quick example, let's assume I wanted to find out a "fair" price for Vigor, I could look on its product page on magiccardmarket to see the following information (this is for the Lorwyn printing): You can see a number of prices, which I'll explain due to the lack of official documentation on the site: From gives you the cheapest price of availability of this card, with at least Excellent condition Foils from does the same, only counting Foils Price Trend is a fictional number, calculated from recent average selling prices per day the graph on the right illustrates recent prices and also shows the Price Trend, which is helpful to see recent developments - this will also let you gauge whether you can trust the previous figures Now, all of these values need to be taken with a grain of salt, as so far, this includes all sellers registered on the site
It is also a great way to not only authenticate your card but to also preserve the condition