What practical/efficient algorithms exist for minimum weighted set cover problem (MIN-WSCP)?
One possibility is to use the standard greedy algorithm.  It can be adapted to weighted set cover by counting the total weight of previously uncovered elements that will be covered by adding a particular set, instead of counting the number of such elements.  This is standard and covered in standard textbooks and resources.  Another option is to use linear programming or integer linear programming.  A little research on set cover approximation algorithms will find much more that is written on the subject.  In the future, I suggest doing more research before asking here.