It's difficult to put an exact figure on it as varying amounts would bring me different sorts of joy. (I am already very happy with my life and have a comfortable lifestyle - for now.) As I work on yearly contracts a large amount, say a few million USD, would be the perfect way to ensure a secure long term future for myself and still allow me to share my good fortune with needy friends. Having said that, I'd be happy to get a windfall that had less zeros.