Because items are obtained at random through opening Cases, rarer items fetch the highest value on the open marketplaces. Items of lower-rarity tiers can also be traded in at volume for an item of a higher tier via trade up contracts. Previously, Knives and Gloves could not be obtained through trade up contracts, exponentially increasing their value as highly sought-after items. Prior to the most recent update, some Knives, like a Doppler Ruby Butterfly Knife, could fetch around $20,000 on third-party storefronts like CSFloat.
Following Valve's Oct. 22 update to Counter-Strike, the second-highest-tier, Covert (Red), can now be traded up and turned into Knives and Gloves. Essentially, this means that a previously extremely rare and highly sought-after cosmetic is going to be much more obtainable for those who increasingly want it, reducing the value of Knives and Gloves on the open marketplace. And this is where the market descends into a freefall. Now, that Butterfly Knife mentioned above? It's going for around $12,000, as people are essentially dumping their stock, with 15 sold over the past 16 hours at the time of this writing.