Negotiation is an art. Weighing interests and making judgment of whether the deal is a deal or it's an energy-sapping undertaking with no returns.
Some essentials of making a negotiation include having a strong case for yourself and not appearing like a begger looking for underserved favors.
If it's a worth venture, it should not come cheap. All high quality productions cost an arm and a leg. If they were not costly, everyone would be having such, driving down the basic rules of demand and supply.
There are terms that need not be varied lest they cancel the current contract and new one is negotiated or it's ended. Of course, some issues get ironed out by good communication rather than a top-down method that is coarcive rather than collaborative.