You found an old card and you want to know what it is worth. You open an app, type in the name, and get a number. But is that number accurate? It depends on the card, the app, and how you use it. Most pricing apps pull data from recent sales on platforms like eBay and TCGPlayer. For modern cards this works great. There are hundreds of sales per day for popular cards, so the data is solid and current. Vintage cards are a different story. A Base Set holographic card from 1999 might only sell a few times per month. If the most recent sale happened to be unusually high (maybe two bidders got into a war), the app shows an inflated price. If it sold low (maybe the listing had bad photos), the app shows a deflated price.