Complex sentence: The series is a spin-off of 2009's "Iris" and has been budgeted at 20 billion won ($17 million USD) like its predecessor, making them the two most expensive Korean dramas ever produced.
Split into simpler sentences: The series is a spin-off of 2009's "Iris". After having been budgeted at 20 billion won ($17 million USD) like its predecessor, the two series have become the most expensive Korean dramas ever produced.