Here is a link to an interesting and useful article which provides some insights into how to determine the time it takes to develop e-learning resources.
This is something we have to explain to clients when creating e-learning resources using SCORM creation tools, developing graphic design content, and producing course materials.
The Time Tracking Template is quite simple, but effective for basic instructional design, and might be useful for you too ? You could use any spreadsheet such as Excel or LibreOffice Calc for this.
Worth following is the link to Bryan Chapman’s research for some complementary data: http://christytucker.wordpress.com/2014/03/18/time-estimates-for-e-learning-development/