Today (Monday) Microsoft announced that we are going to a unified price worldwide for OneNote 2003. Until today, OneNote was $99.95 in Japan, and USD$199.95 everywhere else. In the US and Canada there was a rebate coupon for USD$100 off (CDN$150), which effectively made the price $99.95, but you had to deal with the rebate.
The new price is a simple $99.95 worldwide, which means the rest of the world (e.g. Europe) can get the lower price currently being enjoyed in Japan and the US.
With a new product you have to experiment a bit to see where the pricing sweet spot is, and $99 seems to be it based on the amazing response we are getting in Japan in particular, which had the lower price from the start. Keep in mind that although the price change is effective immediately, not every brick and mortar retail store will jump up and change the price tags on the boxes so you may not see the new price if you run to the store tomorrow morning - as I am sure you will do after reading this :-)
Academic pricing is still $49, and if you plan to buy in large quantities you can get a volume license ("large" means 5 or more). From comments I hear it sounds like a lot of people don't realize that you can get discounts if you are buying OneNote for a small office or workgroup. For details see this page.
Jeremy Wagstaff picked up the price change. You can read his comments here. He also wrote a very nice article about OneNote in the Wall Street Journal and the Far Eastern Economic review. These are premium content but if you subscribe you can read them. Here's a link to the FEER article (http://feer.com/articles/2004/0408_05/p036innov.html)