Trade-in means that when consumers buy new goods, if they can give the same kind of secondhand goods to the store, they can get a certain price discount, and the secondhand goods play the role of discount coupons; If consumers can't submit old goods, new goods can only be sold at the original price.

For manufacturers or merchants who use the old-for-new promotion method, the recycled secondhand goods usually have no economic value; The purpose of exchanging old goods for new ones is mainly to eliminate the sales obstacles formed by second-hand goods, and to prevent consumers from buying new goods because they are reluctant to discard used second-hand goods. At present, the trade-in promotion is very popular, involving bicycles, watches, household appliances, furniture, housing, gold jewelry, pressure cookers, water heaters, gas stoves and so on. Even suits, sweaters, sneakers, woks, etc. , can be replaced with new ones.