Halliday & Matthiessen (1999: 277):
In the construction of meaning in economics, economic things such as prices, salaries, yields, financing are quantities. At the same time, they are also elastic bodies that grow and shrink; and also ‘mountaineers’, climbing up and down slopes. This at one level an impossible conjunction: things cannot be both quantities and mobile elastic bodies — but the semantic system of English makes this possible through lexicogrammatical metaphor. This proliferation of perspectives is part of the semogenic power of metaphor.