man with shellfish kanji
This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development of 价 is uncertain. It visually combines 亻 (person) with 介, but the original role of these components is unclear.
The given meaning is vague. Picture a person 亻 holding a shellfish 介, but treat the meaning as uncertain.
For カイ, the right side 介 itself can be read カイ, so remember the reading by associating it with 介: 介 -> カイ.