Tea, n, 1
c. Phrases. given away with a pound of tea: see GIVE v. 54a; not for all the tea in China (colloq., orig. Austral.): not at any price.
1937 PARTRIDGE Dict. Slang 148/1 China!, not for all the tea in, certainly not!; on no account: Australian coll.: from the 1890’s. 1943 K. TENNANT Ride on Stranger ii. 19 I’m not going to stand in my girl’s light for all the tea in China. 1958 J. CANNAN And be Villain vi. 137 She wouldn’t get into a sidecar or on a pillion for all the tea in China. 1978 Radio Times 11-24 Mar. 25/5, I wouldn’t change Newcastle for all the tea in China… It’s a lovely place to live in.
I’m a little dubious about the Australian origin, especially as the phrase ‘would have pleased her better than all the tea in China’ occurs in Sir Walter Scott’s Rob Roy, first published 1817. (Google book search). Yes, the phrase is ’not for all the tea in China’, but I’d put good money on that form turning up in print in England long before it appears as an 1890s Australian colloquialism.