Game: the Alchemist's Self-Cultivation

Yan Shaohan accidentally traveled to the game "Eternal Day" he played in his previous life and became an NPC, an alchemist in Novice Village. "Boss, is it really okay for you to sell me this level of medicine for ten gold coins? Are you sure this is not a black shop?" "Buy it or not, I'm the only alchemist around here." "Okay, I'll buy it." "Boss, your fourth-level potion costs me 100 gold coins, while others only sell it for 80 gold coins." "You can choose another store and leave as soon as possible if you don't want to buy it." "Can't I just buy it?" "Boss, the seventh-level potion you sold me for 800 gold coins is not much different from the seventh-level potion for 500." "Look, you are a bit superficial. I can buy unlimited potions. You can only buy one potion for 500 gold coins a week. Is one enough for you?" "800 Is too expensive, can it be cheaper?" "If you like it, buy it, if you don't, go away." "I buy it, I buy it."