The Sorare card economy is a real economy with a real price chart. The price of a card is set by supply (rarity tier and edition count) and demand (the player's projected minutes, the upcoming fixtures, and the manager community's sentiment).
What moves a card's price
Three things move a card's price: a transfer to a bigger club, a long injury absence, and a run of decisive performances. A transfer to a bigger club usually raises the price; an injury usually lowers it. A run of form raises it, but only if the form is sustainable and not a four-match hot streak.
How to read a price chart
Look at the median sale price, not the headline sale. A Unique card that auctions once at a season's reserve does not tell you the market price; it tells you that one buyer was prepared to pay the ceiling. The median sale over the last thirty days is the most reliable signal.
Common mistakes
The most common mistake is buying on a hot streak. The second most common mistake is panic-selling on a dip. Both reduce long-term returns. A better discipline is to set a target price before you bid, walk away when the price exceeds it, and never list a card in a panic.