Preparation is your greatest leverage in lowering cost.
I provide a full breakdown (using ChatGPT and my experience) of exactly what I want the designer to do, down to the order of the sections and the copy within it. That is less work and headache for the designer, and so you can negotiate lower prices.
With that visual design, you give the full layout to the developer, which answers a ton of questions and makes it a more desirable project to work on, which again allows you to negotiate lower prices.
I do this everytime I outsource work. By doing things in this way, the people you are hiring enjoy working with you because you are very clear and give them everything they need upfront, so it is less headache for them, and that is leverage in negotiations for you.