K-pop became hyper-commercialised as its popularity spread around the world and music industry executives realised that they could make a profit from the loyalty of hardcore fans, one analyst said. One of the most prized possessions of public relations executive Valerie Chan is a black spiral-bound album. In it are photocards of the members from K-pop group BTS, their faces lovingly protected by transparent PVC-free plastic sleeves and housed in individual card slots. The most expensive card