The idea of paid content, as with anything is that; it's more informative, you get more, more in depth, personal experiences, maybe 1-1 tutor, downloads, additional resources, etc etc.
I would like to point out however that Udemy has a lot of free content, some good, some not so good but free none the less.
It's your job to find out what's relevant and what's not, what learning style is best for you. And personally, if you're going to learn something - do it with a project you want to do (as complex and farfetched as you like), not a TODO MVC or some other generic crap that you don't learn anything from because it doesn't show you anything.
Learning should be fun :).