Indeed, Istio is very CPU heavy and probably not great for cloud use on a truly large scale just due to cost concerns. Shopify found it uses 50% more CPU then an alternative like Linkerd [1]. Istio also incurs much larger latency and lower throughput then Linkerd [2]. (To be clear, I don't have a dog in this Istio vs Linkerd fight, those are just some recent benchmarks I'm aware of)

[1] https://medium.com/@michael_87395/benchmarking-istio-linkerd...

[2] https://medium.com/@ihcsim/linkerd-2-0-and-istio-performance...