Redeeming s'dei achuzah

Question

This has bothered me for many years - but I am not even sure of the right question to ask!
The Torah at the end of Parshas Bechukosai (Vayikra 27:16-22) describes the law of makdish s'dei achuzah (consecrating one's ancestral field) and how to redeem it. It is clear from verse 18 וחישב לו... עד שנת היובל ונגרע מערכך that we are picturing the object being redeemed as the field until yoveil. That is what is worth 50 shekel, that "rental" [this is an averaged value, like many things in that section]. He could redeem it shortly before yoveil, and it might cost only one shekel, depending.
Now that he has redeemed it, he keeps the field forever after yoveil, something that is clearly worth a lot more than 50 shekel.
However, if he doesn't redeem it at all, or if the gizbar sells it to anyone else at any point before (verses 20-21), then he will never get it back, and it goes to the cohanim after that yoveil.
It comes out in a way that seems very "uneven" to me: by redeeming the value of the field till yoveil (<= 50 shekel, plus a chomesh), he is actually buying back the use of the field forever (much more than 50 shekel). It is as if he is redeeming a s'dei mikneh, but receiving a s'dei achuzah!
As I said, I'm not sure of the right question, but how do others understand this?

Answer 1

Erkekha on Sede-achuza is not an action that has something to do with real-estate business. Sede-achuza gets a fixed value, that has nothing to do with it's market value:

ואם משדה אחזתו יקדיש איש ליהוה והיה ערכך לפי זרעו זרע חמר שערים בחמשים שקל כסף

If anyone consecrates to the LORD any land that he holds, its assessment shall be in accordance with its seed requirement: fifty shekels of silver to a ḥomer of barley seed.

Also, look at the previous verses on the same Parash that use the exact same term:

...איש כי יפלא נדר בערכך נפשת ליהוה והיה ערכך הזכר מבן עשרים שנה ועד בן־ששים שנה והיה ערכך חמשים שקל כסף בשקל הקדש ואם־נקבה הוא והיה ערכך שלשים שקל ... ואם־מך הוא מערכך והעמידו לפני הכהן והעריך אתו הכהן על־פי אשר תשיג יד הנדר יעריכנו הכהן

... When anyone explicitly vows to the LORD the equivalent for a human being, the following scale shall apply: If it is a male from twenty to sixty years of age, the equivalent is fifty shekels of silver by the sanctuary weight; if it is a female, the equivalent is thirty shekels. ... But if one cannot afford the equivalent, he shall be presented before the priest, and the priest shall assess him; the priest shall assess him according to what the vower can afford.

Well, these values do not reflect the actual condition of the person, other then he's\her's age and gender, right? Also, you get consideration if you are poor?! That's not how you do business! So Erkekha is just a way to make a donation to beis Hamikdash, and not about getting good deal for the gizbar or the vower .

Answer 2

Just a suggestion toward an answer, but one that helps me at least not be as bothered.
As some of the answers and comments pointed out, the Torah has a number of responses when something is made hekdesh. Maybe I'll divide them into two main classes:
1) Things like cherem - the object becomes hekdesh and never goes back to the owner at all. A korbon is mostly similar, unless it gets a mum.
2) Things like arachim, where the object isn't meant to be hekdesh; the hekdesh is just a way to make a monetary contribution.
The point of the first is to give away the object. By cherem the Torah emphasizes that it never comes back (לא יגאל).
The point of the second is to make a donation. Perhaps doing it in this way shows one's love or appreciation to Hashem for the object. The gemara in Arachim has more examples, "nidri alay", "mishkli alay" (giving his value, giving his weight) along with the Torah's "erki alay": various implementations of the same idea.
Most cases of hekdesh could be either. When a person is makdish his donkey, or his field, he might be doing one of two things: really giving away the donkey or field, or using it to make a monetary contribution. If the latter, he would redeem it right away. That's different from anyone else buying it from hekdesh; only he is the "owner", only he pays a chomesh along with the value. (There's a well-known Shiltei Giborim somewhere who says that even arachim itself is a momentary hekdesh on the person, immediately removed and replaced by a debt...)
[There is a third possibility: he planned to give it away forever, and then changed his mind. In that case he would be using pidyon as a way to undo his mistake.]
In the case of s'dei achuzah, probably the gizbar is going to try and sell the field right away. If so, this man needed to plan this from the first, have the money for redemption on hand and ready. He is makdish and redeems, back to back. If so, he would be implementing the second possibility, using this as a way to make a donation focused around this field.
[See the discussion Arachim 30b if he is even allowed to borrow money to redeem it.]
This way of picturing things helps me feel better about the "unevenness" issue. When he redeems, he is not "saving himself a lot of money", as my question suggested. The Torah is talking about two different people, one giving away his field forever [where the money is beside the point, and indeed it might be impossible to place a true value], another who isn't doing that at all.
[Of course, plans can change, and the person can belatedly try to switch paths in the middle, if the gizbar is slow enough. I don't know if that affects what I'm saying.]