I follow Korean pop culture more than Japan's, but I definitely have a sense that the K-POP labels have virtual stables of up and coming "properties", getting paid little, living in bunks with other stars-in-training and eating instant noodles, but being given the very best in song and dance lessons for hours a day, waiting to be selected by their manager to begin a nationwide PR blitz and concert series for at least 2 years of "instant" stardom, then cultural obscurity.
I imagine that something no entirely dissimilar happens in the U.S., but the feeder system is all different...
The K-Pop starlet BoA is one I remember very well (also semi-popular in Japan if I understand correctly), chosen at about 13 (years ago), dropped out of school and "manufactured" through endless training programs to become what she is today. Interestingly, she was an investment by her label specifically for export to the U.S. and Japan. She hasn't done well in the States, but her label seems happy with her performance across the Sea of Japan, infiltrating J-Pop. Her interviews in the States (in very good, but accented English) came across as weird, slightly aloof, uncomfortable and detached...kind of what you'd expect out of somebody who has never really lived a normal life.