There's something I don't understand. What's to prevent me from buying a bunch of goods, which will raise the price in the city, and then immediately selling those goods for profit? Seems like you could just stay in one spot buying and selling the same stuff over and over, making a bunch of cash in the process.

Am I missing something obvious?

Thanks!

Doesn't work, try it :D
If you do it like this, you'll loose money
The price you are buy or sell stuff is allways after the deal.
Thats also the reason why some players sell their stuff if they have much of it in small parts.
There is also another problem. If other users are seeing that prices go up, they come and sell their stuff too.