Responses
Daughter sacrificed the love between her and the merchant to the crystal ball thing to turn herself human. That merchant, no longer in love with mermaid, tried to sell her back to the fish man for 4K in gold. MC broke the crystal, she turned fish again, merchant loved her again. No more 4k price tag.
A bit confused but in chapter 3, basically the daughter mermaid coerced her own father for money? Is that why the mc shot the crystal ball in the end?