How is the financial loss from the Suez canal blockage calculated?

Welcome to “Economics is not a hard science 101”.

I think they mean mainly in terms of losses to the impact on the expectations of international corporations, and the supposed value of the cargo that was scheduled to pass through the canal. Of course it’s not really possible to objectively answer that question; one needs to select a perspective. There’s going to be a certain amount of delay in time, a certain amount of actual waste and damage which may have certain costs for certain people, and endless other types of impact, none of which are really reducible to a one-dimensional dollar amount unless you select a perspective that only cares about the impact of specific accounts.

News companies like to say an monetary amount of damage because it sounds like a sensational fact.

Companies like people to frame events in terms of monetary costs to themselves, so they can claim hardship and sue/petition for legal advantages or insurance compensation or whatever. This is often grossly inflated for that purpose, such as when they try to spin copyright violations as if it’s monetary damage being caused them every time someone makes a mixtape, because supposedly if they hadn’t made a mixtape, they would have instead re-bought multiple albums at list price. LOL