[puzzle]

Google probably got back a lot of the engineering costs before it even rented out the first TPU, simply by virtue of running its own workloads, without having to buy tons of CPUs or GPUs. They're also very, very good at reducing computing resource waste (I know this firsthand).

I wouldn't be surprised if public TPUs are to some degree a way to print money: at least for a while, Google can probably just rent out its unused capacity that it had already planned and paid for. :-)