Each Google K80s is one GPU or 1/2 of a K80 board, so technically you are correct that a Google K80 GPU is half of a K80 board. However, they are offered in passthrough mode and achieve full performance. If you want a whole K80 board, attach 2 K80 GPUs to a single VM. You can have 1, 2, 4 or 8 K80 GPUs attached to each VM in GCP. (I'm one of the GPU product managers at Google Cloud).

It would be polite to indicate that on the price list (understatement).

While you're here: the other reason we switched to Hetzner is reliability. Sure we can continue training from the last checkpoint but we still lost half a day on average for the many surprise reboots. We suspect that you've overbooked the GPUs and someone has to lose when too many connect.

The price list indicates that 1 instance is 1/2 a device, and so on: https://cloud.google.com/compute/pricing#gpus

Although I agree it is somewhat confusing in terms of performance.

thanks for the info. On a side note, do you know if GCP will ever support preemptible GPU instances?

According to this[1] comment it's on their mind but doesn't seem like a priority.

[1] https://news.ycombinator.com/item?id=14728476

They clearly state this, the K80 contains two "GPUs", when you get one K80 instance you only get one of those two GPUs, so you get half of a K80.