Gemara

(Mishnah): Embarrassment is evaluated according to the one who embarrassed and the one who was embarrassed;

To evaluate blemish, we appraise how much less one would pay to buy her to be a slave (because she is not a virgin);

Gemara - Question: How do we evaluate this?

Answer (Shmuel's father): We evaluate the difference between what one would pay for a virgin slave and a non-virgin.

Question: One buys a slave for work. Why does he care whether or not she is a virgin?

Answer: He has a male slave whom he like, and he wants to give to him a virgin to marry.

Bava Kama 90b (Mishnah): A case occurred in which a man uncovered a woman's head in the market. R. Akiva obligated him to pay 400. R. Akiva agreed to give the man time to pay.

The man broke a small flask of oil in front of her. She uncovered her hair to dab the oil into her hair. The man had witnesses see this, and claimed that he should not pay 400 Zuz (since she herself uncovers her hair for trifling reason).

R. Akiva: That is no claim. A person may not injure himself, but if he does, he is exempt. Others may not injure him, if they do, they are liable.

Rishonim

Rif and Rosh (Kesuvos 14a and 3:7,8): Embarrassment is evaluated according to the one who embarrassed and the one who was embarrassed. We evaluate blemish as if she was a slave being sold. We evaluate the difference between what one would pay for a virgin slave and a non-virgin, to marry her to his slave whom he likes.

Ran (DH Masnisin Iy): Rashi says that if an average person embarrassed, this is worse than if a lowly or honorable person embarrassed. One pays more for embarrassing an honorable person. It seems that this applies to other matters, but regarding rape and seduction, the more lowly the man, the greater the embarrassment.

Rosh: We evaluate the difference of what one would pay for this woman if she was a virgin or not. Each woman is evaluated based on her worth and her family.

Rambam (Hilchos Na'arah Besulah 2:4): Embarrassment is evaluated according to the one who embarrassed and the one who was embarrassed. One who embarrasses a distinguished Na'arah from a family of good lineage is unlike one who embarrasses a poor disgraced minor. A distinguished man who embarrasses is unlike a lowly man who embarrasses.

Rambam (5): The judges evaluate his and her standing and evaluate how much money her father and family would have paid to avoid this from happening. He must pay this much.

Rambam (6): We evaluate blemish based on her beauty. We evaluate her like a slave being sold, and calculate the difference between what one would pay for her if she was a virgin or a non-virgin, to marry her to his slave whose benefit he seeks. He pays this amount.

Rambam (Hilchos Chovel u'Mazik 3:1): Embarrassment is evaluated according to the one who embarrassed and the one who was embarrassed. Being embarrassed by a lowly person is unlike being embarrassed by a great person. The former is greater.

Question (Tosfos 40b DH Kamah): How can we say that a woman from a prestigious family is blemished only like a Shifchah?

Answer (Tosfos): Indeed, we consider how much a master would pay for a woman of her prestige before and after the Bi'ah. The Gemara discusses a Shifchah only because it is not common to marry a princess to one's slave.

Drishah (EH 177:6 and Bach DH u'Mah she'Chosav Pegam): Normally, a man does not pay a woman to marry himself or his son. Rather, she brings a dowry! Therefore, it discusses a slave. Alternatively, it is a big stringency against the seducer to consider how much one would pay to marry her to his slave. One would not need to pay so much to marry her himself.

Poskim

Shulchan Aruch (EH 177:1): If one seduced a Besulas Yisrael (Rema - from three years until Bagrus), he pays embarrassment, blemish and a fine.

Taz (2): If the girl was lewd, her embarrassment is smaller than that of a Tzenu'ah Bas Yisrael. It seems that even if we see her act lewdly afterwards, we may assume that she was this way even beforehand. We learn from Bava Kama. Even though the woman herself uncovered her hair, R. Akiva obligated the man to pay 400 Zuz because a person is allowed to harm himself. If not, he would have been exempt. We do not say that only now she began to act immodestly!

Shulchan Aruch (CM 420:24): Embarrassment is evaluated according to the one who embarrassed and the one who was embarrassed. Being embarrassed by a lowly person is unlike being embarrassed by a great person. The former is greater.

Rema: Similarly, if a more dignified person is embarrassed, the embarrassment is greater. If a Kohen was embarrassed, the embarrassment is greater than that of someone else.

Question (SMA 25 and Prishah EH 177:5): Rashi (Kesuvos 40a) and the Ran both say that (in matters other than rape or seduction) the greatest embarrassment is from an average person. The Tur and Shulchan Aruch are unlike either of them!

Answer (Prishah CM 420 and Gra 420:30): The Tur and Shulchan Aruch are like Rashi in Bava Kama (83b DH ha'Kol) and the Rambam.

Bach (DH Boshes): Perhaps Rashi in Kesuvos meant that embarrassment is greatest from an average person only regarding rape or seduction. (This would resolve the contradiction in Rashi.) However, this is totally opposite to the Ran!