Ah the cruelties of imperfect information! Damn you imperfect information, and take price discrimination down there with you!  FLASH, economics in action right here right now in Shenzhen.  So I was out buying presents, which is more difficult than it sounds, trying to find things that are distinctly chinese and yet not the exact same stuff that I saw all the time in Chinatown, especially in Shenzhen, which is not noted for its tourist trade so there are not alot of stores catering to that sort of thing, not that most of the stuff in said stores would be anything but kitsch anyways.  Anyways, back to the point at hand.  While in beijing a friend had bought a t shirt for 50 kuai, about 6 bucks and was very happy about it until I showed him the same shirt that I had bought for 15 kuai.  While he was upset I pointed out that since both he and the seller had reached a mutually beneficial  arrangement, where they had eached exchanged an item for something they wanted more that it was an okay deal.  According to utility maximization, perfect price discrimination works out well, where each customer pays exactly how much for the item that it is worth to them.  So when it happened to him it was actually okay in the grand economic scheme of things.
Because of imperfect information, there exists price discrimination outside of a monopoly and inside of Shenzhen.  The shoes that I bought in this example, while still cheaper than how much i would have paid for them in the USA were still much more expensive than they would have been had I known the other prices they were being sold for.  Ah, economics, you are a cruel cruel mistress!!
Also on an unrelated note, I was asked why I had a new hotplate.  The old hotplate did work, after a fashion.  It would work well for about 10 to 15 minutes and then shut off for another 15 minutes until I could turn it on again.  So I bought a new one, and the old one will go to a needy fellow teacher whose school only gave them a microwave so everyone ends up happy.  Almost done teaching my week about being on a deserted island and I am going to put a full blog entry into the asnwers to questions I got about that but I did get to teach them the word cannibal so there is a preview.