This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development of 賯 is uncertain. It combines 貝 (shell/money) with 㝁, but the origin and original meaning are unclear.
The left side 貝 suggests value or money, and the right side 㝁 is obscure. Without a clear meaning, picture a mysterious treasure chest: 貝 hints at treasure, and the unknown shape keeps its meaning hidden.
For ケイ, imagine a treasure chest locked with a key: key -> ケイ, and the 貝 component hints at the treasure inside.