We have HTTP ingress that needs ~100 cores but could theoretically all fit in 1GB. We have k/v stores that need only 16 cores but would like 500GB. And we have data points at most places in-between. We can't give the ingress 600GB instead, and we can't give the k/v stores 100 cores. So the fact they're financially interchangeable is meaningless for capacity planning.
Arguably, for most code and especially in a GCd language, using less memory and less CPU go hand-in-hand.
