With Aespa and now NewJeans, we have seen explosive growth of sales, without equal growth of other metrics like MV likes on YT. The most obvious explanation is that the sales are coming from China, since they don't use YT. Particularly C-bars who bulk order. It's seems like China is the next big market you need to be in, like how SM focused on Japan in the early 2000's to explode sales.
For example HYLT has 23M likes and their album sold about 3 million counting digitals. Aespa's girls will probably be around 3M likes at the same age but their sales are about 1.7M now (let's say 2M at the same age to be very conservative). That's a proportion of about 7.7 and 1.5 likes/sales. Even using LSG, their less popular single from the album, you get 4.7, 3x Aespa. That's a huge difference.