Consumption is the sole end and purpose of all production

See Conclusion of the Mercantile System which is Book IV, Chapter VIII of The Wealth of Nations by Adam Smith. From Library of Economics and Liberty.

"Consumption is the sole end and purpose of all production; and the interest of the producer ought to be attended to only so far as it may be necessary for promoting that of the consumer. The maxim is so perfectly self-evident that it would be absurd to attempt to prove it. But in the mercantile system the interest of the consumer is almost constantly sacrificed to that of the producer; and it seems to consider production, and not consumption, as the ultimate end and object of all industry and commerce.

In the restraints upon the importation of all foreign commodities which can come into competition with those of our own growth or manufacture, the interest of the home-consumer is evidently sacrificed to that of the producer. It is altogether for the benefit of the latter that the former is obliged to pay that enhancement of price which this monopoly almost always occasions."