The value of בתולים

This observation shows how the value that the Torah assigns to a woman's virginity remains constant throughout the Torah

We find in the Torah (shemos 22:15-16) that if a man takes a woman’s virginity via seduction, he’s required to either marry her or pay her מהר הבתולות if her father doesn’t care for the match.

 How much does that amount to? 

Chazal (b kesuvos 10a) look to the instance of where a virgin is raped where the Torah requires the rapist to pay 50 kesef (devarim 22:29) to determine how much the relatively benign fellow over in parshas mishpatim needs to shell out.

It seems that the monetary value of a woman’s virginity was 50 shekalim and therefore whenever a fellow takes them, he needs to pay up. 

There’s another case (devarim 22:13-21) where a husband accuses his new wife of not being a virgin where if he’s found lying he must pay 100 kesef — twice what the rapist pays. 

Rambam explains (Moreh 3:49) that the kesubah was valued at 50 kesef and that this husband, instead of divorcing her and paying her what she’s entitled to is instead trying to rip her off by claiming that she's not entitled to the standard virgin kesubah payment (as he claims to not have found her to be a virgin).

The Torah levies a double payment (shemos 22:17) on thieves—once to pay for the item stolen, and once as a fine for what he tried to do to his fellow. 

Here too the devious husband is treated as a thief and pays twice the usual virgin kesubah payment  (Rambam loc cit).

What emerges from all the above is that virginity has a constant value of 50 kesef.

If a man takes that from a woman outside the context of marriage, for which it is ostensibly vouchsafed, or even within a marriage but subsequently the marriage ends either via divorce or the husband's death, he’s obligated to compensate her for the valuable virgin status that he’s taken from her, as he isn't (any longer) providing her with marriage in return.