The vendor gave Firey a candy apple for free. Himmel Soan wanted to turn him down, but Firey had already accepted it and taken a bite.
He couldn't give it back now because he couldn't turn the apple back to its original state. He only smiled in resignation. Although he didn't have any essence stones to pay for it, he did have the cores.
Back at the village, Oech told him that the cores and essence stones were both valuable objects that could be used as money here.
Cores were the more valuable one of the two. Since he didn't have any essence stones, they should do the trick.
After some consideration, Himmel Soan took out a core that was halfway between yellow and pale-orange.
He obtained it after killing the giant bear and found it suitable to pay for the candy apple.
"Can I pay with this?" Himmel Soan asked.
If Oech was right, this core had to be worth more than the candy apple. But he didn't know if the vendor would accept it.