Can you point to a training mission where multiple aircraft & refueling flying tankers cross half the globe to drop multiple huge, presumably very expensive bombs ?

I doubt they are conducted that often at this scale.

They do it all the time with simulated targets and ordnance.

I'm just a civilian on the internet but the total cost was much much more than a just the bomber flight. Getting the equipment and related crews across the globe to the target in a highly secure way is non-trivial. Just based on public info the preparations for potential retaliation were significant across many different US properties in the region and abroad.