After developing a short animation piece for a client, I send them an invoice for $800. I originally gave the client an estimate of $750.

Client: “I have a problem with this invoice. I agreed to $750; this is for $800.”

Me: “Perhaps, but I gave you an estimate, not a quote.”

Client: “We’ll have to talk about this.”

Me: “I told you the cost would be “around $750”, and it’s just $50 off based on the hours required after a few of your revisions. I’d say that’s a pretty good estimate.”

Client: “We’ll have to talk about this.”