Unless you make a very foolish purchase, you can anticipate something close to 100% resale by buying used speakers. This applies to virtually all brands and models, current production thru classics.
Top resale value speakers
When you consider buying a new pair of speakers, the sound, outlook and review of the speakers are important, but resale value of speaker is also a important thing to consider before your purchase. Some of the speakers resell value drop so deeply, but some don't. Can you suggest some high resale value speaker company? As far as I know, B&W have a pretty strong resale value compare with their brand, such as Dynaudio, Proac or JMLabs.