
Negotiation is not only haggling over price. It is agreeing a way of working that suits both sides. A supplier who earns a little and respects you is better than one who loses on you and cuts corners.
If the terms do not suit you or the supplier dodges questions, it is better to step away politely and move to the next. That is why you always keep a short list.
Write a negotiation sheet for your product: what I want, what I accept, what I will not accept. Try reading it aloud as if you were talking to the supplier.