The value of any item connected to a musician or musicians depends on who it is and what the item is. Letters, autographs, personal items, can be of interest depending on how unique the items are. Sheet music, especially if it is an original publication from the era prior to the recording revolution is highly sought. Obscure or peculiar objects, while they may generate curiosity, have limited value, unless they cross fields of interest. If this is the case, multiple collectors will be seeking to acquire the item(s).
The value of posters is an interesting phenomenon. Mass produced posters that saturated the market at any given time carry less appeal because of their abundance. However, original posters designed by artists of note are always in demand. That being said, simple prints on cheap stock that were distributed and posted to promote a musician or band, especially if they are from early in their history, have risen significantly in value. The condition of the posters is critical to maintaining their value.
Patch collecting, like pin collecting, has a large following. Despite this, the value of patches rises slowly, if at all. As with other collectibles, the popularity of the musician or group, and the significance of the event are the ultimate determinants of value. A large collection of patches devoted to a single artist will generate interest than single random patches.
Novelty items from the music and entertainment industry have mixed levels of interest. Complete lunch boxes promoting certain iconic characters are in great demand, as are vintage music memorabilia. Popularity, condition, and scarcity are important in determining value. One way to get an idea as to the desirability of a novelty is to visit auction sites looking for comparable items. Monitoring the bidding for them is a good way to tell is an object is worth collecting.
The collectability of concert memorabilia rests on a number of factors. The historical significance of the show (the first or last performance), what the memorabilia is (equipment, instruments, posters, etc.) and the availability of similar items. Autographed items are more desirable than non-autographed items, and original printed products are better than reproductions.
Clothing and other apparel associated with greats in the music industry can have mixed appeal. The degree of fame or notoriety of the individual in question provides the greatest boost to value. Autographed items are also highly desired. Apparel from certain landmark events, concerts, or recording sessions will generate interest, especially if documents that validate the item accompany it.