Cost to relocate stairs

We have a second story house with stairs at the far back. It makes for an awkward use of space - one room is just a "walk through" room to get to the stairs. I know it will vary a ton, but any ideas what to expect-ish to build new stairs/relocate existing ones? We are in San Mateo County.

Edit - we want to add another bathroom upstairs, and open up the main level too. Moving the stairs will allow the "walk through room" to be an enclosed bedroom rather than a large useless room. I am in touch with design / build firms, and working on getting quotes, but the question I keep getting is "what is my budget" and I honestly have no idea what to expect. I'm in the Bay Area so I don't know what "very expensive" actually means here.