As a filmmaker, one of your top priorities when planning the making of your film will be staying within your budget. So many film projects exceed their original budget, which can lead to a host of problems further down the line. By making sure that you are aware of how to stay on budget during casting through the smart negotiation of actors' contracts, you can potentially save a significant amount of funds.
Decisions made on casting will involve many different factors, including the prominence of the actor, the suitability of them to the given role, and, of course, their required salary. It is likely that compromises will need to be made in some way or another, but through good bargaining techniques, you may be able to negotiate a salary to your advantage.