China spends an estimated $100 million a year on cloud-seeding efforts that include using anti-aircraft guns and rocket launchers to blast the sky with silver iodide.
No indication of the source for that number, but it was reported in an Associated Press story on dealing with drought around the world (here via LA Times), and was contrasted with a figure of $15 million for the U.S.
China has had a lot of drought to contend with over the past couple of years, notably in the grain-growing and increasingly arid North China Plain, and is frequently said to do more cloud seeding to induce rain and snowfall than any other country. Of course, you need the clouds to seed in the first place. They are usually absent during a drought, so cloud seeding can amplify rain but not abort a drought by itself. So one strategy might be, say, to make it snow in October and store the melted run-off in reservoirs. Oh.