I am absolutely not knowledgeable enough on the problem, but other than a company calculating a crude price for e.g. a hospital — that will generally over or undervalue it by a lot (like I don’t even know how many public tenders are won by a company in Hungary, only to increase the price 10-100 folds and the promised timeframe by 3-10 times. This way legitimate companies with more correct pricing loose at the tender already, while these corrupt ones can do this indefinitely leeching on our money (and our stupidity to vote for this corrupt party yet over again))

In a very idealistic system they can may know the availability of concrete, of this specific tool, etc. And we can’t ever know whether an alternative building in its place would have been better — like that doesn’t happen under capitalism either.