Blizzard has started testing the Real Money Auction House in the public beta last week and I'm a bit late to the party in commenting about this new development. While testing how the auction house works with real money is a positive thing, I doubt it will show the whole picture.
Blizzard has loaded up testers' accounts with what they call Beta Bucks, a virtual currency that's supposed to simulate actual money. I don't see any other way in which they could have publicly tested this feature. However, bear in mind that those 50 Beta Bucks are universal across all geographical zones, meaning that people in the US got 50 BBs, people in Europe got 50 BBs, people in Brazil got 50 BBs and people in Asia got 50 BBs.
It's quite obvious that in reality these Beta Bucks aren't equal to actual money. In fact, we can view them as just another virtual currency, same as gold, or, if you will, a type of super-gold. From what I understand, the gold AH is not enabled in this iteration of the beta. This, unfortunately, prevents testers from experimenting with the relationship between gold and Beta Bucks (or real money if you will). At the same time, this consists one of the reasons why I don't think Beta Bucks will be an accurate indicator of how people on the actual RMAH will behave.
The second reason has to deal with human nature. Consider these cases:
a) give someone the option to spend $50 of their money on virtual items, if they want to. Most people would think twice before doing that. Some would spend just a small amount. Some would even decline to spend a single cent.
b) give someone $50, tell them they can only spend it on virtual items. Everyone would spend that cash since at this point it acts exactly like virtual currency: it has no value in the real world. However, some people would be more selective in what they would buy with that money.
c) give someone 50 Beta Bucks (or Beta Ducks or whatever) and more people would spend it with abandon, especially if they know that later they might be given some extra Ducks when they run out. Yes, apparently Blizzard hinted at that.
My point is that people's behavior will change depending on how they got their hands on that money. People are more likely to spend virtual currency that doesn't have any value in the real world, even if they have worked hard for it. They are even more likely to spend the same virtual currency if they got it for free. They are less likely to spend real money that they've worked hard for. They are more likely than that to spend real money that they got for free.
While testing the auction house with something that resembles a real currency is better than not testing it at all, we need to keep in mind that people will behave differently when they need to spend their own money. Because this is something that hasn't been attempted before in an online game, the real RMAH testing will come in the months following Diablo 3's release.