Economics assumes that, IN GENERAL, people act rationally. Not every person is perfectly rational, and no individual person is rational 100% of the time. But in general, people make rational decisions when spending money. Of course there are also the issues of how well informed people are, as well as impulse control and other psychological considerations. But lets at least get the basics right before the econ bashing continues.
Econ is far from perfect; And the real world is too complex and chaotic for economists to easily predict much of anything. But video game economies are vastly simpler. Sadly, as has been said repeatedly... what this game has is not an economy at all. It's more like a pretty picture that kind of looks like an economy if you don't really know what an economy should look like.
It's my experience that people, in general, act irrationally (me included

) with their pocketbook

Also, I'm not bashing economics, as I actually do enjoy the entire study of the economy (and it helps pad the stocks if you know what I mean). Of course, I've only had formal training in a microeconomics course, but I have went through all of the MIT / opencourseware in all the economics stuff they had (I am by no means a "real economist"). I just think that psychology is a quite a bit more important in the study of a functional economy than most people state.
At least, my approach to economics, stocks, and bonds has made quite a bit of money; mostly theoretical (stock watching), but now in reality (actually trading). For some reason, my cousin, who is a professional stock broker, keeps asking me what my stock picks are whenever there is a family get-together. My first pick was Qualcomm, right before the cell phone market hit. All cellphones had a "Digital made by qualcom" chip in them. The stock went from $3-4 upwards to $400 and split several times, iirc. It's been awhile. Another one was the screen manufacturer that Apple used. Picked a few of those right when the Iphone 1 arrived. Anyways, back to the day job.