Komentarz do Arachin 3:1

יש בערכין להקל ולהחמיר וכו' – all of them are explained further on in our chapter.

The law of evaluation is sometimes lenient, and at others times strict.
The law of the field of possession is sometimes lenient, and at others times strict.
The law concerning a warned ox that has killed a slave is sometimes lenient, and at others times strict.
The law of the rapist and the seducer and the defamer is sometimes lenient, and at others times strict.
The law of evaluation is sometimes lenient, and at others times strict. How so? Whether one has evaluated the fairest in Israel, or the ugliest in Israel, he must pay fifty selas. But if he said: “Behold, his monetary worth is upon me,” he pays only as much as he is worth.
Like the second chapter, the third chapter also begins with a discussion of evaluations and through associative thinking goes on to discuss other laws that have a similar phenomenon. In this case, the phenomenon is that sometimes the law is lenient and sometimes it is strict.
Sections 2-4 will be explained in mishnayot 2-5, so I will not explain them here.
Section five: This section demonstrates how sometimes the laws of evaluation are strict and sometimes they are lenient. If a person vows the evaluation of a very good looking person, one who might be worth more than 50 selas, he still owes only 50 selas, because the Torah determines the person’s value as such. This is a leniency. But if the person is ugly and is really worth less than 50 selas, the vower still pays 50 selas. This is a stringency. We should note that this is true as long as the person’s whose worth is being donated is a male between the ages of 20 and 50. For older and younger males and for females, the evaluation is different. Nevertheless, the principle would be the same for all.
As we explained in the introduction, if the vower uses the word “monetary worth” instead of “value” then he owes the actual worth, be it higher for the good looking person, or lower for the ugly person.

את הנאה שבישראל – even if he is worth one-hundred Maneh, he does not give other than fifty Selah, and that is rule leniently. And to rule stringently, that a person pledges the valuation of the ugliest among the Israelites, even that he is not worth anything other than five Selah. He gives fifty Selah if the person being valuated is between the ages of twenty and sixty.