Because COCOON is usually in Asia they had problems with authors not coming to the conference which leads to an interesting paragraph in the author's instructions pointed out to me by a student author.
Each accepted paper must come with a full registration (i.e. not the student rate) for the paper to be included in the proceedings. [The full registration rate is 450USD, the student rate is 250USD.] For authors with multiple accepted papers, one full registration can "cover" up to 3 papers.I understand what COCOON is trying to accomplish but why punish the students with an extra $200.
In general authors make a pledge to come to a conference if their paper gets accepted and COCOON is just reacting to authors who don't fulfill that basic commitment. So paying a registration fee (not to mention travel costs) is essentially a requirement if you want your paper to appear in any conference proceedings. In CS, a field that puts greater prestige on conferences than most journals, that puts a heavy burden on those who want to publish their papers but do not have grants or other travel funds available.