I think for most places and most workloads, the state of the art in cost estimation is “figure out the fixed costs, see that they’re reasonable, then launch and keep an eye on the first few bills to hope all the bandwidth and other “surcharge type” costs aren’t deal-breakers...”
This doesn’t work when the cloud marketing associates this as a “cost of doing business”
Which causes revenue chasing and profit hunting to “stay alive”.
Not to mention the massive startup credits issued which ensure complete and utter lock-in for the entirety of your business’s existence (successful or not).