Price increases at Elsevier hybrid journals

Elsevier’s hybrid or sponsored-article journals promise to reduce their subscription prices in proportion to author uptake of the OA option.  („We do not plan to charge subscribers for author sponsored content.“)  But at the same time they raise their subscription prices every year, as usual.  How does this net out? 

William Walsh has put together a very useful table showing that Elsevier’s hybrid OA journals raised their subscription prices by 6.39% last year, even more than the 5.5% increase at Elsevier journals overall.  The company did not reveal the rate of author uptake for the hybrid journals. 

Comment.  Can Elsevier verify that it actually reduced prices in proportion to author uptake?  Can it explain why the hybrid journal prices nevertheless rose faster than the company average?  Will subscribers press the company to answer these questions before renewing again?