Surely a great achievement. Although I feel a little bad for the team. I assume Silver didn't write all the code or design the entire algorithm single-handedly. But the recognition and the reward accrues to him alone. Ah, unjust hierarchical society.
I guess the other members of the team are being compensated well enough at DeepMind that $250k would be more icing than cake, but it still feels weird to see that Silver is the only person named in the article when a number of other world class researchers worked with him on this problem.