That's not how litigation works. It is not zero cost for the plaintiff. It is not all "sunk cost."

Besides that they usually hire outside counsel who are used to doing litigation, If that firm isn't based in the city where the suit was filed, then they hire local counsel who's appeared in front of that judge.

There are court costs, witness costs, deposition expenses... it goes on and on. It is definitely not handled all in-house by the Monster legal team.