Cost efficiency is always important, regardless of your total resources.
The preemptibles are just used for the rollouts — i.e. to run copies of the model and the game. The training and parameter storage is not done with preemptibles.
If these (or other similar) experiments would show viability of this network architecture, the cost could be decreased a lot with development of even more specialized hardware.
Also one could look at the cost of the custom development of bots and AIs using other more specialized techniques: sure, it might require more processing power to train this network, but it will not require as much specialized human interaction to adapt this network to a different task. In which case, the human labor cost is decreased significantly, even if initial processing costs are higher. So in a way you guys do actually optimize cost efficiency.
Cost efficiency is always important, regardless of your total resources.
The preemptibles are just used for the rollouts — i.e. to run copies of the model and the game. The training and parameter storage is not done with preemptibles.