Rough estimates are not possible for the reasons you mentioned, too many variables.Your location, permits, availability and quality of contractors, condition of your walls etc all play into factor.When they ran the wires, the knobs would keep them off the frame and prevent them from electrifying the wood.Tubes were used when the wires needed to go through joists.
The difference could be due to replacement of other wiring around the old boxes.
Our electrician said they have some sort of tool to snake out the old wires and replace the new ones through the "already there" outlets to minimize damage to walls.
Anywho, haven't done this yet, but thought something we were told might be helpful. [email protected], Shannon is right on with her information although I would say that the estimate for replacement of the main service panel and upgrading of the service to today's standards is a bit high in my experience.
Someone told us that because we have plaster walls this is a big deal. That sounds more like a breaker or receptacle problem than a wiring problem. If you do need rewiring most interior wood frame walls are hollow and wire can be fished through, though it may be necessary to make small openings here and there to fish from floor to floor or around duct work, plumbing, or other obstructions.
We were under the impression that the electrician could just thread the new wiring through the wall but our friend told us they have to tear down the plaster walls. Are we really looking at having to go through putting up new walls in addition to new wiring?! If your electrician says otherwise, visit with a different craftsman.