Imagine a world where you would have to pay for each word you spoke or wrote. I wondered which words (or which kind of) would be the most expensive ones? I assume it would not only be a matter of frequency, but also the quality of expression would be relevant. Likewise, there would also be words which are "cheap". So by which criteria would you determine the value of words in such a world?
EDIT: Иво Недев made a good point, so let us assume that it is not possible to invent new words, unless they are published by the government (like in a 1984 scenario).
EDIT: Concerning prices, let us assume a free market. The government only determines the words. (Javert proposed another scenario, a dictatorship, which would have a completely different impact on this question. Answers could discuss this as well.)