It looks like it isn't surprisingly affordable on Amazon. If I'm reading this right, EKS is 20c an hour per cluster, or about $150/month, and that's before EC2 costs for the actual machines in the cluster.
If you further use spot instances (the equivalent here to "preemptible") you can save a ton more.
The real savings (or $7 per month) is that on GCE you won't need to run your control server. GCE does that for you for free.
Edit: now another issue here is (and I have no idea if this is true for GCE like it is AWS). t2 instances will throttle you if you use too much CPU which can be an issue when running a lot of containers.