I am not sure the gain is in the world cup itself. However, if you can set up central qualification cities to play, that would do much more for travelling. It would be a back and forth travelling cost incurred for several teams, but instead of 1 match it would be three matches, which would limit travelling severely. Obviously there is the discussion over home advantage then.
I agree on the building costs though. Upgrading stadiums which would have happened anyway, is still a burden, but less so than building existing stadiums up from zero.
Travel to and from the World Cup is another one where you could gain. Qatar is an odd one here since it is difficult accesible, but going from Europe and Asia to Russia might have been an option by train. It just takes a little longer, but deal with that.