The data was calculated on a 5-person boy group with about 3 years of trainee experience. As it is unlikely that an idol group will be popular right from the start, the investment was calculated into their 2nd or 3rd release.
A 3-year trainee period for a 5-person group costs 700-900 million KRW (656,000-843,000 USD). A 3-song album (a single) costs about 27 million KRW (approximately 25,000 USD) with 15 million going into composers and 12 million into recording costs. An MV, on average, costs 150 million KRW (140,000 USD), but can cost much higher. Album jacket filming costs 20 million KRW (18,700 USD), while marketing costs 105 million KRW (98,300 USD). Processing costs 2 million KRW (1,900 USD). Music show promotions cost 500 million KRW (470,000 USD), calculated for a 5-person group going on 24 music shows all with different outfits. The breakdown is 5 million KRW for choreography (4,700 USD), 10 million KRW to pay back dancers (9,400 USD), 170 million KRW for outfits (160,000 USD), and 10 million KRW for makeup and hair (9,400 USD).
It's reported that most labels, small or big, have similar costs to debut an idol group. Based on this, if an idol group does not manage to succeed within 2-3 years, their debt can build up over 1 billion KRW (940,000 USD).
Because of this, many smaller labels cannot afford to keep pushing idols that don't succeed, which is why there are so many idols that don't make it. Not only so, an idol group has to do very well to break even and actually start making money - for example, we know that MONSTA X broke even only recently. (However, it is also known that even in MONSTA X, Wonho, who has the longest trainee period in the group and therefore the most debt, has not yet broken even. Normally, he would not be getting paid - however, he's revealed at a fansigning that Starship Entertainment didn't feel right not paying him while the other members were, and has worked something out.)
What do you think about all the costs?