I've been tempted to not reply to this because honestly there are a lot of people who have no idea what they are talking about, and I don't want to start a flame war on a site with people I know and love

However:
@joniee I guess I'm kidding myself then. I don't put too much time into Diablo 3 and I make more than any job I've ever had. Oh, did I mention it's fun (to me)?
@purehybrid While I have a character capable of tackling Act 3 Inferno, I generally don't 'farm' it in any way, shape or form. While my Auction slots are full, then I will play - until I get that lovely email telling me something has sold.
@TheBard I love this post, I love knowing that there are people in china making $20 an hour plus playing this game and that that is huge money compared to what they could earn there natively.
@Ralph Like I said, there isn't any farming involved in Arbitrage - it's buying and selling, not just selling. I get that it doesn't seem fun, but people feel the same way about manufacturing and market hunting in EVE, don't they? Some of us just like to play the game differently.
As for profit over time, I could give out details, but I'd need to turn my spreadsheet into a graph

@Bronze_D You're hugely right about it not lasting. The idea however is to make as much profit as I can during this time so that when the gold rush dies down I can gear so well that Inferno is a fricken snap.
Like this:
http://www.youtube.com/watch?v=4Am7oKBD3PU@bagwan unfortunately that's what happens when you have an extremely slack company when it comes to dealing with bots. 'Oh we banned BLAH amount of accounts' - that's nice, in the month it took you to get off your fat ****, they made enough money to buy 100 more.
@psychosmiley - while I agree with the sentiment entirely, the truth is that like I mentioned above, when bans aren't instant the moment Warden picks up botting activity, they are never going to stop botting. They are earning so much money they can just make another handful of accounts.
@PureHybrid - Ah, the post that made me reply, after this long winded speech I'm no longer 'epic level rage' at your response. Auction house Arbitrage has never been really hit and miss for me. I have not purchased a single item that hasn't made me profit (though on one occassion I was close).
One of the biggest things is knowing items and equipment that sell and who they might sell to. I do a lot of unconventional builds, that require specialist gear, and I know there are a huge amount of players with a similar situation. So what I do is I profit from that.
Truthfully, Arbitrage will only get harder once that Gold:$$$ part of the RMAH goes live, but even then I expect opportunities for Arbitrage will still exist, at least in the early days, and it will be far easier to turn my $$ into gold, allowing me to have a more steady flow of profit. Not bad either way.
The final part? Sluggishly? Really? This was three hours while I was asleep:

Yeah, real sluggish.