Spending about 880k gold (including gems) for an entire equipment good enough to allow you to kill triple champion packs in Act 3. Check this video where I do it with the gear I just bought in this one : http://youtu.be/_hAfXfHAC5Y With better gear, you can kill triple packs in 20s : http://youtu.be/5nayhzdLGKo
As I said at the beginning of the video, I'm focusing completely on defense/survivability (it even ends up being a bit of an overkill in the end), so the DPS end up being pretty low.
But still, you can tank in Act 3 no problem, kill packs before their enrage timer and farm with very few deaths, if you're patient. Or you can go in Act 2 and farm faster. Or spend a bit more gold and get some Strength in addition to the defensive stats on some pieces, boosting your DPS a lot, since my Strength is ridiculous there.