100th of yen
錢 centers on a small monetary unit: one hundredth of a yen, a very small amount of money.
錢 combines 金 (metal, gold) with 戔, which likely contributes the sound and relates to smallness or cutting, suggesting small metal coins.
The left side is metal 金, and the right side 戔 looks like two small spears. Picture tiny metal spearheads used as small change: 錢 is a tiny fraction of a yen.
For セン, imagine a tiny coin worth one cent: cent -> セン, and that cent is one hundredth of a yen.