CS:GO skins and all other Steam Market items are subject to a $400 maximum listing price. Items are often sold for greater sums through key trades, a sub-currency of the CS:GO economy. A single CS:GO key costs $2.50 USD and can be sold on the Steam Marketplace. To break through the $400 ceiling, you convert your listing price to a key value. If you want to sell an item for $500, divide your listing price by the key value, 500 by 2.5: 200 keys. Most people use third-party trading websites to list CS:GO’s rarest wares, but once a trade is made, those keys can be sold back into the Steam Marketplace.