Killing Floor 2 is getting its own in-game marketplace where you can purchase goods with real money. Dubbed The Trading Floor, the shop vendors cosmetic items like clothing and weapon skins, which will drop at random during gameplay and can be traded with fellow zombie-killing enthusiasts
These drops will come in crates, which need a "decryption key" to unlock. "Horzine supply crates contain a single skin variant of a wearable cosmetic, chosen at random from a set of possible items for each type of crate," Tripwire explains. Those decryption keys can be purchased either on the Trading Floor directly or via the Steam Market. In addition to skin types of various levels of rarity, crates might also drop a "precious golden accessory".
Again, you'll be able to trade items with other players, but in the future you'll be able to break down loot and craft exactly what you want. Tripwire doesn't explain how this will work, but it'll come in a future update.
To reiterate, these items are cosmetic only. "All of the content added in Trading Floor at launch will be cosmetic only and not affect gameplay in any way," Tripwire writes. "In the future we may be adding weapons with new gameplay for sale, but this will appear in the “Shared Content” area on the server. This means that, if any player on the server has a weapon (like the Chivalry Zweihander now), then every player on the server will be able to use it. No-one gets any “advantage”. Co-op game - everyone starts out equal! Our goal is for any such weapons to be side grades anyway, so they won’t provide an edge over the current tier of weapon power."