Green’s Dictionary of Slang

(Aus.) expensive.

1992		Sydney Morn. Herald 19 Jan. 132/4: Comments like ‘good but exxy’ wines [...] are common.
2001		Sydney Morn. Herald 27 Mar. 43/3: The cohort declares it one of the best ways to peel her precious parmesan. ‘Exy’ (as in expensive) but sexy.
2014		Google Book Review On Line 14 Mar. 🌐 Sorry, exxi (or exy or exxy) is Australian slang for expensive.