Thoreau argues that the real cost of a possession should be measured not only in money, but in the portion of a person’s life required to obtain and maintain it. Income represents time and labour, so acquiring material goods may demand hours, years or continuing obligations that could otherwise be used differently.

In Walden, this idea supports Thoreau’s wider criticism of unnecessary consumption and excessive material commitments. He asks readers to consider whether possessions are worth the labour and dependence they require, rather than assuming that greater wealth automatically produces a better life. His definition of cost therefore resembles the idea of opportunity cost, but gives it a personal and philosophical dimension: every expenditure can also represent an exchange of limited time and freedom. The quote encourages people to judge material choices by the life required to sustain them as well as by their monetary price.