Do summoned units count towards victory points?
No, they do not. 

As you said, they did not cost anything to inlude in the army so are worth zero (unless the unit has a rule that states otherwise).

In addition to which, many summoning spells explicitly state this.

For example, Raise Dead:


  Units summoned by this spell cannot be dispelled, and do not award
  victory points under any circumstances. (Vampire Counts 8th Edition, pg 60.)