Some of these cards, like limited edition cards, shiny Pokemon, and so on, are extremely valuable and command high prices, but it's important to make sure you that you're purchasing old or used cards from reputable dealers when shopping online
Your number can fluctuate a fair amount otherwise, but mana rocks and supporting artifacts as a theme by volume are the two tentpoles that cause radical shifts in the number, which will in turn affect your counts most for cards in the various colors
2014: Treasure Cruise from Khans of Tarkir As much as I'd like to pick my old friend Siege Rhino, which was a legitimately great Standard card at the time, it's hard to consider a good four-drop with a Lightning Helixlike enters trigger a truly broken card
Then create a 1/1 red and white Soldier creature token with haste for each muster counter on this enchantment
Quick fake-detection checklist: Measure width and height against 2.5 x 3.5 (63.5mm x 88.9mm) Check thickness against ~0.30mm Inspect corner rounding for consistency Hold up to light and check for the opaque black core Compare weight against a known genuine card (~1.8 grams) If a card fails two or more of these checks, treat it as counterfeit until proven otherwise