There are far too many details involved in rewiring an old home to expect an accurate estimate in a forum such as this. Besides, unless the person answering the question works in your area, any number may well be meaningless.

As for patching, that's something you need to work out with the electrical contractor. Old plaster repairs might well be left to a plaster expert, not an electrician.

"What would be the reasonable price? Should plaster / drywall
Finish included?"

Unless you hire a general contractor to handle the job do not expect the electrical contractor to do more than make recommendations.

An experienced GC can help you balance plaster damage against increased labor for the electrical work.

It takes longer to do electrical while minimizing plaster damage.
Actual plasterers are not inexpensive either.

A balance between fishing electrical cables and simply bashing holes in plaster walls needs to be struck.

If my cousin's experience was any guideline to DC electrician's prices, then 50K would be about ballpark for a small residence. And then there's the plumbing..... HVAC......... Foundation......... roof........

DC is very much a city of HAVES and then HAVE NOT's. There really isn't any middle ground. And the prices reflect it.

*&^ I thought DC meant direct current at first.

"There really isn't any middle ground."

There are huge expanses of middle class and upper middle class housing in Washington, DC.

The government is doing its best to drive them out though.