The number is checkable. Almost nobody checks.
A spec sheet counts physical cores. Cloud rents vCPUs. Different unit, and once you allow for how many virtual CPUs share a physical one, the gap between what the sheet says and what the workload actually needs is routinely bigger than either number on its own suggests.
That difference is one line of a quote. It is enough on its own to make cloud look expensive when it isn't.
Most of what gets provisioned runs nowhere near the size it was bought at. So a like-for-like quote sizes the packaging, and the number comes back high. The only way to know the real figure is to watch it: a week or two of live data across the busy periods, read through more than one assessment tool, because they rarely agree and the disagreement is where the real number hides.
A while back I said the spec is usually a guess. This is the part I left out: how you check it, and why the vendor who just types the numbers back into the tender still tends to win. A tender scores line-item compliance and price. Almost nobody reads the technical pages.
Full write-up on the site. Link in the comments.