You haven't gotten any answers yet because there are so many variables that an estimate is not possible without seeing it. Even then, surprises come up!
A wall touches the ceiling, floor, and another wall - all of which will need to be blended, repaired, or replaced.
A wall contains electrical outlets and wiring, sometimes plumbing, and in my personal experience an old chimney (Surprise!!).
Opening up a wall is often worthwhile from an enjoyment aspect, and market appeal when it comes time to sell. It takes pros on site to estimate how the renovation will work out from a return on investment angle.
All the Best,
Jim Sweat, ABR, CRS, GRI, CDPE, e-PRO, ILHM