I was looking for an Arduino Uno prior to my RasPi purchase and found several Canadian suppliers. One such supplier (http://www.canakit.com) has the Arduino priced at $29. However, after taxes and shipping using standard mail ($12.95) we are up to $48.47. With express mail we add on $29 for a total price of $66.61, almost the cost of my RasPi!
My local dealer also has the Arduino Uno which I can buy directly in-store, however the cost is still in the $40 range no matter how you cut it. I guess they all must pay a shipping fee and import tax, so by the time it is offered for sale at your local electronics shop it will be in that range too.
RasPi or Arduino?
One of the advantages of the Arduino is the extremely low power usage, and also once it is programmed it can be turned on and off and simply resume the program very quickly. The Raspberry Pi uses more power, has to boot the entire OS (which could take a minute) and you would need to configure a boot script to automatically load the program you wish to run, in case of power failure. Otherwise it would just load up to the desktop or Linux terminal and sit there waiting for input.
On the other hand, for only a few bucks more ($20 let's say, after all taxes/duties/shipping) you get a fully-functioning computer with the RasPi that you can interact with and program directly. It also has ethernet built-in so you can theoretically create a program that could also send messages to (and receive) from the internet. Arduino can do that but only with an add-on ethernet board. Your RasPi can also power a display, unlike the Arduino which also requires an add-on video board.
Truth is, they are different animals and can compliment each other. However, for the small difference in price the RasPi seems to offer way more functionality yet still give hackers the option to use the GPIO to perform some interesting tricks.