I do think it's worthwhile. Not only for the intrinsic value of joining the organization, but if you ever want to participate in your hospital's clinical ladder or advance in your career, joining a professional organization will be expected.
Can you get a student membership? They also do bank account debits each month rather than a one time payment. Your choice. I was recommended to become involved in AWHONN, and take as many classes as possible to show employers that I am interested and willing to be involved. Magazines come in the mail, unless you choose the online versions.