A basic 12x15 basement can be finished for about $10,500. Every basement I've finished gets more use than any other portion of the house.
The Westchester job is my most recent basement job. I took 5 rolls of film and got shots of before, during and after. The quality of the photos could be better but at least you can get a general idea.
I Converted this basement to an apartment but didn't take any photographs. I'm not finished yet and am now using it as my office. When I get a chance I will take some photos of what I did and I will take some of the work that I do to finish.