Some flights run totally empty (airlines need to keep their precious routes) which uses a marginally smaller amount of fuel than a full plane, but provides no real value (nobody was transported to a location they wanted to be in). Other flights are normal, but also carry an individual of great importance, or play a strategic role.

Some training runs waste a bunch of power and then get thrown away. Others go on to serve users and make billions of dollars.

The energy cost is only a proxy for the fully loaded "value" of what you create with your energy consumption. That's why it's not comparable.