BT21 is indeed the most innovative and creative that BigHit has ever made to maximize the company's profit. Even with Seokjin (Jin) and Yoongi’s (Suga) bad assumption, TATA, which was created by BTS V, becomes the most popular and profitable character of all BT21 characters. Multiple proofs can be found easily to see how success TATA is among all BT21 characters.
Here’s another proof (showing the beginning inventory from each merchandise) from sales in China on Taobao website that will make TATA’s credibility on its popularity becomes unquestionable. Despite having the bigger stock than the rest (and sometimes the highest price), TATA manages to sell out first.
There are multiple batches of sales happening in China and TATA series still have the biggest stock. Imagine how much TaTa is profitable for BTS V, BigHit and LineFriends. TaTa is so popular that LineFriends always put a different and bigger stock for its merches.