Don't be silly, a Go AI has very little direct value for Google's business. But the publicity is great, easily worth $1M. More important is keeping the DeepMind team busy and engaged -- the real value is in spinning that know-how off into other projects.
> Don't be silly, a Go AI has very little direct value for Google's business.
On the other hand: Knowing what makes some problems much easier for humans than for computers can have direct value on Google's business. Go was a hot candidate for a game with this property.