Your cost will be the amount you pay someone to do it. Anyone else has done something else somewhere else. Rely on the estimates you are getting or do the project yourself and you will either save money or see how much a bargain $9,000 is.

What about buying 1 or 2 doors that fill the rough opening + a few inches for overlap? Looking at "barn doors" I see that even my local home store has these doors http://www.homedepot.com/b/Doors-Windows-Doors-Interior-Closet-Doors-Barn-Doors/N-5yc1vZcazi.

Then, you'll just have to buy and install the boor door sliding hardware for above the space.

Id be hesitant to do a barn door on what I assume is a small master if there isnt enough room for a swinging door. I believe they are quite trendy and in a few years you might be tired of it and stuck with this huge thing. I like them in very particular settings usually on big farm houses. Just something to think about.

it can be A lot of work....This Barn Door is h-h-Heavy, we had to open up the wall inside the bathroom , and add a new header and cripplers to handle the weight, ( span both L&R/Opened and Closed.) this incurs drywall, painting, trim , jamb work ...and the door and hardware it adds up if you are doing it properly -best of luck.

post edited: for clarity