This I believe. From print media days, I was told by an industry insider the "make your model with free parts every month" magazine churn was enormous, they were in profit from part 2, which is why they even hit "part 2 free with part 1" because they didn't want to admit parts 3 onward weren't coming. The sell was to ad-land, to all intents and purposes the customer didn't exist beyond the first sell. Could be rockets, cakestands, wedding dress or cookoo clocks. Same model same outcome.