When the RMAH was initially announced, many players were getting enthusiastic about getting rich from the game. I for one, was very skeptical about this for the very simple reason that you are offering a service that other players can easily do themselves. For example, if someone owns a burger place it makes sense that you pay $10 for a burger because they are offering a service you cannot do (at least not when outside!), but it doesn't make sense that you pay someone for gold or items when you can easily get the yourself.
Of course, there exceptions such as people who don't want to farm, or ultra-high stat items that people will buy, but these are few and far between. There was at least one guy on the official forums that said he spent $800 on the game, but the thread has been deleted. The way I reasoned it, is that on average players would get 1 good item per hour, which sells for about $5-8 on the RMAH. $8 an hours isn't something you look forward too right?
It seems I was wrong however, as a Diablo 3 player who goes by the name of WishboneTheDog on Reddit claimed he made $10,000 from the RMAH! To back up this incredible statement, he also posted screenshots of his RMAH and Paypal transaction screens:


Note: The blurred transaction is a gold sale he made directly to a person. He did not want to reveal his name.



Some of these values are amazing! I never thought anyone would actually pay $200 for a virtual item, but as you can see from the above screenshots it actually happens a lot!
The player claims that economics were always his favorite part of games, starting 10 years ago when he use to trade on NeoPets (I used to play this too!). Since that time, he has taken to a more serious approach to the subject and is studying business at an unknown university.
He has answered many questions regarding the subject on the original Reddit post, with the exception of which items he sold and some other secrets, because "it's part of what makes me successful".
One Reddit user that goes by name of ardentatheist asked him about his play time, country of origin, etc, which raveled some interesting points.
According to his direct answer to the question, WishboneTheDog claims he played on average 8 hours a day on release, sometimes even 14! 8 hours is standard for most jobs, but 14 hours would get the employer arrested for breaking work laws! He also said that his playtime has dropped a lot lately mainly due to the slowing in-game economy (ie. lack of players) and real life responsibilities. He plays on the US-NS servers but has also sold things on the EU servers for gold.

Another good question was from Reddit user someguy945, that asked if he was going to pay taxes on the money he earned from the game.
WishboneTheDog responded by saying that he was going to pay the full tax amount for the money he earned, mainly "because of my relationship with taxes so far in my life". Other good points that came out from this answer were:
- He has never finished Act 4 Inferno!
- He lost about 250 million gold when Blizzard nerfed the attack speed values on items.
- He has never found any majorly under priced items on the AH mainly due to botters buying them out before him.
The pictures also show another interesting fact. A lot of the items actually didn't sell, which goes to show you that just because he is making money from a game doesn't mean it's all sunshine and rainbows. He must also endure the constant thought of having to re list items, and figuring out why they aren't selling.

He also claims that he has never botted, cheating, or otherwise exploited the game in any way. Pre-Diabo 3 he never actually made any money from games, simply because it was against the rules to sell in-game items on third party sites. It is nice to a see a legit business man actually making money.
So there you have it guys. There is definitely potential for someone to make a living from the game, but I doubt anyone without a lot of time to invest and some economical background will be able to achieve the same results.
The player also put up his email address (wishbonethedog1@gmail.com) for people that want to contact him on the original Reddit post.