An example of catalog spamming, where multiple copies of the same shirt are being sold. Note how there's a different creator for each one, and not all of them sell for the same amount of Robux.
Catalog spamming is the act of players or groups creating hundreds, if not thousands of duplicates of clothing, typically via a bot program. Frequently, the copied clothes are those of a popular designer or clothing set, though it could also be clothing that has been taken off-sale. There are multiple rationales for why catalog spamming occurs. A person with Premium may create a copy of a piece of clothing that is on sale so that they do not need to spend Robux on that item. Some catalog spammers believe players won't investigate whether the clothing is original, either through convenience or no knowledge of who the original designer is. This gives the duplicate clothing creators the opportunity to earn Robux that might have otherwise been spent purchasing the original item. As the original item is rarely identifiable, the duplicate clothing creators are able to set the price of the clothing to be potentially higher than what the original designer is selling it for.
Some catalog spam bots are capable of replacing the clothing template to possibly obscure the original creator. The catalog spamming bots can chain off copies, making it harder to identify content.
Clothing botters may also set the prices of the botted clothings to 5 Robux (the lowest price possible) to gain more purchases, as users would mostly buy the same piece of clothing which has a cheaper price than the same piece of clothing which has a higher price.
Typically, copied items duplicate the names of the original item. There are also bot varieties that add [ORIGINAL] to the front, emojis, or convert the text partially. The description is often full of unrelated tags set by the bot, but they may occasionally be customized to fit the uploader or group, or instead directly copied from the original.
Although waves of catalog spam are still noticeable on some searches, the practice of copying popular clothing and spamming them has died down in 2018, as Roblox revoked the ability to view original templates of clothing, which could be done by subtracting one digit from the clothing ID.
Criticism
Catalog spamming is frequently criticized by both the Roblox designing community and customers. As more duplicate items of a piece of clothing are created, the original creator has less probability of earning the Robux that players spend purchasing the duplicate items. Many designers have created wordmarks in more hidden parts of a character, such as the underside of the torso or the top of the legs, that serves as a part of the original design that identifies it as theirs. A major subset of criticism is Roblox's lack of interest in fixing these botting issues or clothing copying in general.
Users looking to purchase specific clothing heavily criticize this behavior, because users can't find anything but the same item of clothing unless they use another search term, which only shows them one more item of clothing over and over or they can't find the original creator of a piece of clothing since hundreds, if not thousands of copies of the same item have been put up for sale at a similar or higher price.