Thanks for linking my mancave 3rdguy.
Ben, when I was having an addition built onto my house, 11 or so years ago, I had it built with a home office in the attic space above the new media room and master bedroom addition.
I had the builder put in an exhaust fan setup. It's a panasonic whisper quiet 440 cfm fan that is mounted in the attic and has 3 hvac vents, located in the ceiling, connected to it.
It works great! I have poker games up here once a month or so and it does a good job of exhausting the smoke from 8 or 9 guys smoking cigars.
On a regular basis, like right now, I sit up here, have a pipe, a glass of scotch, and peruse the pipe forums on the laptop.
The exhaust fan, associated ducting and vents and labor came in at less than $800 - $1,000 installed.
Full disclosure here, when I do have the room full of cigar smokers, I do crack a couple of windows open to assist with airflow, allowing the fan to pull more smoke out quickly.
Dino