Board Thread:Theories and Speculation/@comment-35080474-20180323012714/@comment-35080474-20180323100541

They make a point in the Gaara Novel that Rasa taught Shigezane Water Release solely so he could mine more Gold, and according to this wiki Suna would trade the Gold Dust if needed when they were desperate. So it's a real they simply have, not something Rasa makes or digs up on a whim.