446k Budget Barb full inferno clear.
http://www.youtube.com/watch?v=S4iBp0S-rT8&feature=plcp
Every piece of gear, and merc gear was bought from AH for a total of 446K gold. Inferno cleared with every single champion, unique, and rare pack killed.
He also has individual videos going over each item he bought and how much he paid for it.
http://www.youtube.com/watch?v=0YZd680H5EE&feature=relmfu
But again, if you watch this guide, notice that he was building strictly for progression, not farming. He doesnt skip any packs at all, kills every single one, but he kites when needed and will switch skills and lose stacks if neccessary in order to progress. Its not not about the drops, its only about progressing in those low gold challenges.
When it comes to farming though its much more expensive because speed is a factor, noone wants to farm that slowly.