charging 50$ for online alone would be a large rip-off. listen to the many people that enjoy paying and they'll probably be able to tell you why you should feel honored for ms to take your money with all the neat stuff it can do and whatever.
personally, i just want to play games online with friends so all those other features are worthless to me. its fun to have, but if i had the option of paying for the features + online gaming vs. just being able to join a game and play online with other people, i'd take the online gaming only option, which ms does not provide.
as a pc gamer, we use a wide variety of software to meet our gaming needs such as skype or ventrillo for voice chat, xfire to see what games your friends are playing, etc. some games have that built in but usually it is of poor quality. steam is probably the closest thing we have to the xbox live experience on the pc (though it is free). the games themselves have the features that xbox live likes to promote, such as inviting your friends into your games, so the games devs take care of these things (or rather have to take care of these things) rather than letting xbox live handle it.
however, since ms is able to control their console as they wish, of course they wouldn't open it up to free alternatives like the pc has. instead, they can "conveniently" bundle all that software into the "xbox live experience" and charge for the convenience while their pr dept is busy convincing you that its worth it. as a little side bonus you get to play games online too.
i personally do not care for xbox live, but if i want to play games online on my 360 with friends, what choice do I have? and that is one of the biggest weaknesses of the 360 is the lack of choices. you either get online gaming + whole bunch of other stuff, or no online gaming. there is no happy medium.