A superior item is one which has a fixed cost for enhancement atttempts at all stages (e.g. Tyrants, Nova).
A regular item is one which is not a superior item (e.g. Superior Gollux equips).
Superior SFE refers to the star force enhancement system for superior equips.
Regular SFE refers to the star force enhancement system for regular equips.
Expected costs and expected destructions
Click here to view a dynamic UI for enhancement costs/destructions.
Thanks to /u/Moootaz for building the page
and making this data available in a much more organized fashion than it used to be.
Details of analysis
March 2017: Previous regular SFE data incorrectly assumed that items which blow up are recovered at the star they blew up at.
The currently existing regular enhancement analysis has not been updated to reflect this error, but everything else in that document is fine.
New regular SFE data now makes the assumption that any items which blow up are restored at the 12th star.