I used to buy 2nd hand racquets and sell my used racquets. But recently, racquet prices has plummeted and used racquets have little or no value. Even branded and new models.
In economics, it's called devaluation.
One website wrote that racquets have about 20% annual devaluation at least in the United States, perhaps used badminton racquets are less advertised in market, hence not much market data or analytics. Link here.
But in other countries where badminton is the national sports, consumers in the resale market have more choices as there are more people playing and collecting racquets. In addition, many fell for the marketing gimmick where they see their favourite players using the racquets.
I remember a few years back when the arcsaber 10 was released, I overheard an Indonesian boy telling his father,'Taufik raket! Taufik raket!'. With the constant persuasion by the boy, the father bought his son a Taufik racquet.
Furthermore with online shops selling discounted, clone or older model racquets for sale, market is flooded with too many racquets. Too many people ended with too many racquets.