What is a negotiated fee schedule?

Could you please elaborate on what a negotiated fee schedule is? How does it differ from a standard fee schedule? In what scenarios might a negotiated fee schedule be more advantageous for both parties involved? What factors would need to be considered when negotiating such a schedule? How does it ensure fairness and transparency in the process? Lastly, what are some potential challenges or drawbacks that could arise from implementing a negotiated fee schedule?