Why does it say that the youth additionally answered? This was his first answer!
Radak #1: He additionally spoke. This is like "v'Anisa v'Amarta" (Devarim 26:5) and the first "va'Ya'an Iyov" (Iyov 3:1), which refer to saying; they are not answers. Also Yonason translated 'Lema'anei' (to say 1 ), and not 'Le'asva' (to answer).
Radak #2: We can explain simply; this was his second answer. Sha'ul had said "let us return" (verse 5), and his youth answered "there is a Navi..."
Yayin ha'Tov explains 'Lema'anei' as 'to answer.' This is like Radak's second Perush.
How much is Reva Shekel?
Rashi citing Targum Yonasan: It is one silver Zuz. Radak - a whole Shekel is four Zuz.
R. Chanina (Yerushalmi Kidushin 1:3), Bereishis Rabah 58:7: All Shekalim mentioned in Nevi'im 1 are Litra (100 Zuz. If so, Reva Shekel is 25 Zuz.)
Mar'eh ha'Panim (on the Yerushalmi): This is unlike R. Yochanan, who says that a Perutah can acquire land; the Halachah follows him. (The Yerushalmi resolved R. Chanina's teaching about Nevi'im. The Halachah does not follow regarding Kesef midnight in the Chumash! - PF)
Why did he say "I will give... he will tell us"?
Malbim: I will give Reva Shekel for the wage of telling us. I am only a servant; I need not give Teshurah. (If you would go to see him, you would need to give Teshurah.)
