Shanghai World Expo 2010

I don't understand why some chinese rush one year in advance to buy a ticket for the World Expo.

"Till the end of the year, the peak day ticket costs 180 yuan, and the standard single-day ticket, 140. Tickets will cost 20 yuan more during the expo."

That's only 12% discount on the futur 160 Yuan ticket and 10% on the 200 Yuan ticket.

Do they expect a shortage of ticket ?