Blogger Horace Dediu was recently asked the following question for MacUser Magazine UK:
The exponential growth of Apple products has to end some time soon doesn’t it? How many high-income buyers for expensive products can there be left for Apple to target?
And this was Horace’s intelligent response:
Trying to calculate the limits to growth is futile. There are limits but they are not calculable and inaccurate estimates don’t offer any useful information.
In 1939 a total of 921 military aircraft were built in the United States. Five years later, in 1944, annual production was 96,318. A question could have been asked by an aviation analyst in 1939 about whether the American aircraft industry could grow. Aircraft, especially multi-engined ones used by the military were _extremely_ expensive. The reason an industry grew exponentially making extraordinarily expensive products was not because of organic demand but because the primary buyers engaged in a cataclysmic global war. In other words, there was a will to buy and hence there came a way to build. Therefore the answer to the question of sustainable growth comes not from an analysis of demand but from an analysis of the consequences of not growing. Not growing would have meant the end of many nation states.
Your question was framed by an implied market categorization: that buyers are either high-income or, presumably, low-income. This is a false dichotomy. Buyers are either needful of a job to be done or not. If the job is important enough, money will be found to hire a product. Sellers of products will also find ways to meet the demand through lower prices and increased capacity. Every product Apple makes used to be out of the reach of all consumers. Whether computers (portable or not), music players and professional grade software, voice recognizing personal assistant cellular phones and tablets are all luxuries or necessities is only a question of timing.
Highly recommend reading the full interview here.