Do anyone related to scientific publishing has experience using EOI's as the identifier for the articles in a journal?
I'm Ed Pentz, Executive Director of Crossref. I don't know anything about EOI so can't comment on it. I did want to correct the information you've been provided. Crossref charges annual membership fees from US$275 to US$50,000 but many smaller members join via a Sponsoring Organization and pay much less - please contact a sponsor if there is one in your country. We charge US$1 per current journal article and US$0.15 for older content. Fees for preprints, books and grants are different - full information on membership and fees is available. We have over 13,000 members in 139 countries so are very inclusive. It's not just about the identifier - registering content with Crossref means it's discoverable along with over 114 million other content items. Feel free to email member@crossref.org with any questions.