I suppose it depends on why you're interested in joining WW. I can definitely see why you aren't interested in doing the weigh in part, so are you just interested in the content? If so, you can access a lot of it for free (yay!) without any investment. If you're trying to actually do the points stuff, there are a LOT of free tools available. (Again, yay!)
I used to do the online, but since I know what to do, I don't see the need to pay for the online tools anymore. That's me. There are forums and stuff, too, but there are free ones online also.
It seems like you may not need to make the investment--but it really does depend on what you'd want out of it.