A common mistake in client negotiations is jumping straight to a price before the scope is actually nailed down, which makes every later scope change feel like a fight instead of a straightforward adjustment.
Flip the order. Get specific about deliverables first, exactly what's included, how many revision rounds, what's explicitly excluded, before a number ever comes up. Once scope is fixed, price becomes a much simpler, more defensible conversation, since it's tied to something concrete rather than a vague sense of "the project."
Use the estimate generator to itemize deliverables line by line rather than quoting a single lump sum, itemized quotes make it obvious what's included and give you clean language for pricing anything added later. If a client wants to negotiate the number down, it's often easier and fairer to negotiate the scope down instead, keeping your rate intact while trimming deliverables to fit their budget.
This same discipline protects you later, too: a tightly scoped agreement is exactly what makes the scope creep clause enforceable when new requests come in mid-project.