Usually '3 apples' or 'one person' or 'a man' are used as description phrases, like: 'I am one man', how come we use phrases (dealing with cost) like the following:
Three dollars is the price
Why are we able to discuss 'three dollars' as if it is some kind of thing being named, I can say 'three men walk into the bar but then I am describing them'.
The normal, unmarked expression would be "The price is three dollars." The speaker and the listener have implicitly agreed that a price exists and the speaker is informing the listener of what that price is.
But consider the following exchange.
How much is this orange.
Three dollars.
Three dollars! Are you kidding me? For one orange?? Three dollars is a rip-off.
Well, three dollars is the price. You can pay it or you can leave.
After the first exchange, both speaker have agreed that "three dollars" is the amount of money under discussion, and the second speaker is informing the first that "three dollar" is the price that he charges for an orange.
So you are right, "Three dollars" is the thing being named, the thing under discussion, and the difference of opinion is whether it is the fair price of an orange, or a rip-off.
This is quite normal, and may be used for emphasis or just because it is "logical".
Three dollars is a fair price to pay for oranges like this, they are very sweet and juicy.
The subject of a sentence whose main verb is "is" (or another form of "To be") need not be a name, and is not in this case. Such a subject is often a descriptive phrase. Some examples might be:
- The red brick building on 24th street is the place where I work.
- George Higgins's last novel was Sandra Nicols Found Dead.
- The period from 30 to 60 is often considered to constitute "middle age".
- The phrase "middle of the night" is not an exact time.
- Impressionist paintings were very popular in the late 19th- and early 20th centuries.
Of course in many other cases the subject consists of a name, but there is no rule that requires a name as the subject of "to be".
