You really need to work with the electrician on this.Alot depends on how busy they are vs. when you need it done.I don't know that you'll do any better by spreading the work out over time,however,I have a carpenter who works for me rainy days only at a reduced rate because he normally works on new framing outdoors.As long as you aren't in a hurry,you can wheel and deal somewhat.

This might be a frustrating answer, but it is impossible and misleading to speak in terms of an "average" price because each installation will differ depending on where the circuit breaker is located, wheteher it has adequate amperage to spare to add a circuit, and the layout/construction of your home. I am not an electrician, but I have done enough electrical work to know that electricians are not just trying to hoodwink you by saying that they cannot give an estimate without visiting the home.