BSD So… why do Bet Shammai require such a high amount of money for Kiddushin?
1) We assume women wouldn’t go for less than a dinar (unless proven otherwise); 2) When the Torah mentions the word “kesef” it means silver, not money. Thus, only a silver dinar would suffice (not the regular copper prutah); 3) An Amma cannot be bought for a prutah, and the same applies to Ishus. 4) Out of respect to women, our Sages instituted that their Ishus should not be acquired by less than a Dinar.