And remember that anything that is considered a structural change will require a permit.
You can call some of these folks to get an idea of what you can do
Sing Sing Construction - 510 748 0699 Chee Chan (a lot of realtors and agents use Chee who is a general contractor)
Check out http://www.luisathertonconstruction.com
Lou Atherton, General Contractor - 510.543.7511
Office: (510) 523-1968
Is there plumbing within the wall void that would need to be moved? This could be costly since it would entail possibly breaking into the foundation.
Are there electrical outlets within the wall on either side? This would require rerouting the electrical
There are too many variables to give anywhere close to an accurate guess....Best bet is to have it assessed by more than 1 licensed contractor and compare bids...
This number could be all over the place. Getting realtor's price guesses is not going to be very helpful. You really need a Licensed Contractor to come look at it. He/she needs to determine if this is a load bearing wall, which would require redistributing the weight load, compensating for the loss of framing that currently exists. This costs more money. And, if it is weight bearing, it would be wise to be sure a permit is taken out for this work, because any future buyer who does their diligence, is going to find out this wall was taken out, and then see it was done without permits, and surely be concerned, (rightfully so). And a load bearing wall removal will require more drawings for the City Building Dept. and take more time.
Also, type of materials, and finishes will make a difference.
My best advice, just have a contractor look at it. I would not rely on any prices given here or anywhere for this work. Too big a range and too many variables.