1) The "per opening" cost will vary widely across electrical contractors and the area that you will be building in. Items taken into consideration are if the home will be wired using NM Romex cable or piped in EMT metal conduit.
2) Assuming NM Romex cable, an average "per opening" cost will be around the $65.00 price. This would not include any 240 volt circuits or 3-way or 4-way wall switches or any ceiling fans. This price would include standard type of wall switches and receptacles. If installing Decora type, add on another $5 for each device.
If installing EMT conduit, an average per opening price would be $80.00
3) Keep in mind that an opening is the device count and/or an empty junction or pull box. For example, a 2 gang wall switch box would be considered as 2 openings and not just 1 opening. A junction box that contains splices will be 1 opening. A pull box would also be considered as 1 opening.
4) A typical 100 or 200 amp service panel will range in price anywhere from $1500 to $2500. The panel/service cost will be in addition to the "per opening" cost. The cost can vary here depending if underground or overhead service and the quantity of AFCI circuit breakers that are required.
5) For any 240 volt circuits, I charge a minimum of $200 for the circuit plus another $75 per opening if the opening is very close to the electrical panel. The cost of a 240 volt circuit will be dependent upon the length of the circuit run, the circuit breaker amperage and the conductor sizes. Longer runs and higher amps will increase the price accordingly.
6) On vaulted ceilings, many contractors will increase the opening price by adding on another $10 or so due to the involved labor and the equipment required to reach higher ceilings.