After a certain time, Nintendo put a price on the Internet Channel. For those who had the trial version, or downloaded before the specified date (I don't know the date), got it for free. Other than that, I think it's 500 points.
Anyone can setup their Wii to access the internet for system updates, news, weather and message-board services. But if you want to use the Opera browser and visit websites, you do have to buy the internet channel.