According to Sporno, why does Yehudah reference 'monetary profit'?

Summary: After all, the point is judgement, not revenge! The answer is that Yehudah doesn't really, literally. But this just goes to show how derash, introduced by Rashi, gets totally ingrained as peshat in our minds.

Post: On a previous post on parashat Vayeshev, in the comment thread:

Maverick said... 

As a serious question: the Sforno says that the brothers judged Yosef to be a Rodef, so they dealt with him. The problem is that Yehudah statement (paraphrase) "lets sell him so we can get some profit from this" doesn't jive with this pshat. If he was a rodef Yehudah should have said "we don't need to kill him, we can sell him."

This is a great illustration of how Rashi sets the peshat, and how hard it is to break free of this understanding. The pasuk, with Rashi:

26. And Judah said to his brothers, "What is the gain if we slay our brother and cover up his blood?		כו. וַיֹּאמֶר יְהוּדָה אֶל אֶחָיו מַה בֶּצַע כִּי נַהֲרֹג אֶת אָחִינוּ וְכִסִּינוּ אֶת דָּמוֹ:
What is the gain: What money [will we profit]? As the Targum renders.		מה בצע: מה ממון, כתרגומו:

This is an extremely tempting explanation to give. It stems from a close reading of the pasuk coupled with an awareness of how betza is sometimes used elsewhere. After all, Yehuda follows up with the suggestion that they sell Yosef to the Yishme'eilim, and they do so, for 20 silver. And we see, for example, in Mishlei 15:27:

כז  עֹכֵר בֵּיתוֹ, בּוֹצֵעַ בָּצַע;    וְשׂוֹנֵא מַתָּנֹת יִחְיֶה.

27 He that is greedy of gain troubleth his own house; but he that hateth gifts shall live.

This is likely what prompted Targum Onkelos to render it as such:

לז,כו וַיֹּאמֶר יְהוּדָה, אֶל-אֶחָיו:  מַה-בֶּצַע, כִּי נַהֲרֹג אֶת-אָחִינוּ, וְכִסִּינוּ, אֶת-דָּמוֹ.

וַאֲמַר יְהוּדָה, לַאֲחוֹהִי:  מָא מָמוֹן נִתְהֲנֵי לַנָא, אֲרֵי נִקְטוֹל יָת אֲחוּנָא, וּנְכַסֵּי, עַל דְּמֵיהּ.

Thus, he translates ma betza as מָא מָמוֹן נִתְהֲנֵי לַנָא, and Rashi follows him. So too renders Targum Yonatan.

But even though this translation is so delicious, peshat is rather unlikely to be in accordance with this. Rather, he is likely simply asking what is the benefit, the profit (in the sense of benefit rather than monetary reward), the point? Compare Tehillim 30:10:

י  מַה-בֶּצַע בְּדָמִי,    בְּרִדְתִּי אֶל-שָׁחַת: הֲיוֹדְךָ עָפָר;    הֲיַגִּיד אֲמִתֶּךָ.

10 'What profit is there in my blood, when I go down to the pit? {N} Shall the dust praise Thee? shall it declare Thy truth?

Such is the position of the pashtan, Ibn Ezra:
[לז, כו]
מה בצע -מה תועלת. 
וקרוב מטעם חפץ. 
וכן: מה בצע בדמי.

and so renders Seforno:

פסוק כומַה בֶּצַע. מַה תּועֶלֶת. כִּי אָמְנָם הַנְּקָמָה תְּכַוֵּן לְאֶחָד מִשְּׁתַּיִם: אִם לְשַׁלֵּם לְעושֵׂי הָרָע, וְהִנֵּה בָּזֶה כִּי נַהֲרג אֶת אָחִינוּ נְשַׁלֵּם רָעָה גַּם לְעַצְמֵנוּ, כִּי יִכְאַב לִבֵּנוּ עַל מִיתָתו וְעַל אַכְזָרִיּוּתֵנוּ נֶגְדּו. וְאִם לְהַפְחִיד אֶת הַנִּשְׁאָרִים שֶׁיִּשְׁמְעוּ וְיִירְאוּ מִלְּהַזִּיק אותָנוּ, הִנֵּה גַּם זֶה הַמִּין מֵהַתּועֶלֶת לא נַשִּׂיג כִּי נַעֲלִים אֶת מִיתָתו. 

"What is the purpose -- for surely revenge is directed towards one of two: if to pay back the one who does evil, behold in this, if we kill our brother, we shall pay evil as well to ourselves, for our hearts will ache over his death and over our cruelty towards him. And if to frighten the ones who remain, that they will hear and fear from harming us, behold that we will not achieve this purpose, for we will conceal his death."

With "purpose" rather than "monetary profit", it is far easier to read Seforno's peshat into this. Regardless of whether we think that the brothers judging him with a din rodef is good peshat.