There are discounts if your instances can be pre-empted: https://cloud.google.com/preemptible-vms/. The pricing isn't variable like EC2 spot instances, however.

Time for me to shamelessly plug my TL;DR blog on Google's Preemptible VMs:

https://medium.com/@thetinot/google-clouds-spot-instances-wi...

From the site:

> You cannot attach GPUs to preemptible instances. GPUs do not receive sustained use discounts.

So sorry, no.

The question didn't even mention GPUs, and there's no reason that what you mention can't change in the future. It was a pointer.