We never negotiate price. I'll give them a fair estimate,if they find someone cheaper,that's fine too.
In the past,I've had builders who wanted a break on price "just to help me out" and "there'll be a LOT more work later"Spec builders are the WORST for this.
I gave them the little over break-even price..and they never call again. The 3 main builders we work for now seldom ask for a price,they call and say "It's ready"
We do elec and plumbing both and can shave a bit off if we get both on the same job,but not much.
Russell