Having been a negotiator in my professional life, I thrive on negotiating in particular circumstances. But not in this hobby. I know the market well having participated in it for over 30 years and hire even today at a high level. But when a provider quotes a price I either accept or decline further discussions.
I agree with what Jamie21 said. I suspect your hires are based on niggling the providers you seek out, but who knows. You are entitled to to do as you please.