The phrase “all the tea in China” is part of a longer phrase that usually includes a negative, for example: “I wouldn’t go there for all the tea in China” – the meaning of this type of phrase is that the speaker will not concede to some proposition at any price, or that no amount of money or benefit would compel him or her to do a particular thing. Here, “all the tea in China” is presented as something that represents a large quantity of something, or that would have a vast value to the speaker.
Generally, English speakers understand the above phrase to be based on the idea that China, being a large country with a cultural association with tea, has a great supply of tea which, in its total sum, would be extremely large and valuable. It’s true that China has traditionally produced a great supply of tea and has exported it abroad. When this colloquial phrase began to be used, many people probably understood that the Chinese sum supply of this commodity would command a high value on a theoretical market.
Although China does produce a lot of tea, some experts contend that the phrase “all the tea in China” may also have to do with historic events related to commerce in China. In the 1840s, following the Opium War, in which foreigners attempted to promote drug smuggling throughout China, the Chinese government signed the Treaty of Nanjing, in which China relinquished certain trade rights. Among the traded commodities that figured into the results of this international agreement, tea was a part of broader set of Chinese products that would have become less profitable as an export.
The phrase “for all the tea in China” should not be confused with another one that is commonly used in parts of English-speaking nations: “what does [x] have to do with the price of tea in China?” This latter phrase, which asks a rhetorical question, has a much different meaning and use. It essentially communicates that the speaker feels a proposed topic is largely irrelevant to the subject at hand.
In this second phrase, “the price of tea in China” is loosely linked to the idea of actual commodities trading, and the inter-related markets theory. Many financial experts can draw lines from one seemingly unconnected financial value to another. Using the example, of Chinese tea values, speakers who use this phrase are indicating that two different ideas are not connected.