TCGPlayer developed a metric called the TCG Market Price for each card that was based on the most recent sales, allowing for near real-time valuation of a card in the same manner as a stock market
At the beginning of combat on your turn, each opponent faces a villainous choice That player sacrifices a creature of their choice, or you create a 3/3 black Dalek artifact creature token with menace
Their effects either Special Summon Spellcaster monsters or manipulate ATK/DEF
Their value comes from a perfect storm of immense power and extreme scarcity, hailing from a time of tiny print runs
If you're patient and strategic about which auctions you target, you can pick up cards below market value
I've been having a great time playing Modern Horizons 3 sealed on MTG Arena (19 wins across three sealed events, baby), and I'm very excited to take these frankly cracked new cards and power up my deeply mid MTG Arena decks (built as they are from the random nonsense I've gotten from MTG Arena codes and my usually dismal draft performance)