You'd make a lot of money on the way to doubling the world's supply. 3000 tons annually just doubles how much we mine, not how much we have; that's more like 190,000 tons. And even if you doubled the total supply instantly, you'd now own half the current value of the world's gold, which would be about $6 trillion.

And of course gold has all sorts of really useful properties, so long term, it'd be worthwhile to make it abundant and cheap.