Trade-in is a system of buying, in which the buyer gives the seller his old, second-hand goods, and gets a discount for the purchase of a new one. A particularly popular "trade-in" system is in the car market.
The exact translation into Russian of the word "trade-in" does not exist yet. The English word "trade" is usually translated as "trade", and the particle "in" means movement inward. That is, if Nikolai Rastorguev, then "trade-in" - zatorguev his car back to the salon and get a discount on a new one?
By the way, in the Soviet times there was a system of "trade-in" when buying TVs, but today you can sell your old TV only on Avito.ru, and on the money you get to buy an iron or a pan. Although with the current shizo-propaganda, the most correct decision is to make a trade-in of your TV set for a dump.