i dunno if anyone else has thought of this or done this, but i tried it out last night...

I have all my guys geared up with naxx gear and heroic gear, so regular instances are really, really easy.
So...i went into trade and shot out a message "willing to run anyone through any northrend instance for 200g per run, you keep all loot, can disenchant if needed and you keep all mats"

I got so many tells from people wanting me to run them through stuff, i make like 1k gold in a few hours.... and got to meet some cool people and show them all about multiboxing.