I'm thinking about going to all three workshops - about $400. Its ~$500 for the workshop plus, which gives you all of their resources including: study guide, theory book, work book, model answer, HSC answers, weekly notes, and you can ring them up and ask questions. I've already got the work and theory book - I don't know about the weekly notes - wouldn't they just be summaries of the textbook? I can look up ecos articles and get heaps from school so... it wouldn't be that helpful.
Apparently 3 of the top 10 ecos students went to the workshops.