The publisher De Gruyter offers a 90% discount for all articles published in journals for which we have a subscription. We only have one medical journal of De Gruyter: Clinical Chemistry and Laboratory Medicine (CCLM). This agreement is valid for the period 2016 - 2018.
This works as follows: upon submitting the article, the author doesn't pay anything. In the following year, De Gruyter will charge the Dutch universities (via SURF) 10% of the normal fee for all of the articles published in open access, but only for 10% of the normal fee. The average author's fee for an article in a De Gruyter journal is € 1,000.
De Gruyter is still working on developing a submission portal for authors, which will clearly indicate what the open access options are.