They don't sell in the same numbers as cars because they sell them too high. Its a very simple economics story really. That they are or were the only entity making tanks, does not make their pricing model (ie a monopoly) an intelligent one? On the contraire, plastic and metal bearings are just that regardless if it goes into a car kit or a tank kit - period. We will never know how many they would have sold at a reduced price because they priced themselves out of a market that Heng Long was quite happy to fill. I don't mean to blow my horn here, but I do hold a MBA and have had all the QBA and graduate economics classes one would ever want to take. The analysis of the tank market and the pricing decision was incorrect over 10 years ago and incorrect still today.