Well, yes, and no.
I'd think to a certain extent you're right that as long as you can connect your wii via wifi or ethernet cable, since you are already paying for netflix on a monthly basis you won't have to pay the add'l 500 points for internet access.
And the wii will connect to the internet to do updates and will run certain programs which require internet access such as the weather and wii store for free but you must have internet access via an ISP.
But to use the wii to surf the web (for doing things like visiting the DIS

), you have to use wii points to buy and download the internet access program just as you would any other other program via wii points. When I did it the cost was 500 points or $5 (but points are only purchaseable in 2,000 point increments). This was a one time charge.