What does 1 Samuel 17:27 mean?

This verse describes the answer to David's question (Isaiah 17:26). Philistines and Israelites are gathered for war near the Valley of Elah (1 Samuel 17:1–3, 19). The Philistines sent a champion, Goliath of Gath, to challenge the Israelites to a representative fight. If an Israelite could kill Goliath, the Philistines would serve Israel. If not, Israel would serve the Philistines (1 Samuel 17:8–10). The fight would not be fair. Goliath was nearly ten feet—three meters—tall, covered in body armor, and fitted with an impressive sword (1 Samuel 17:4–7). He taunted the Israelites twice a day for forty days (1 Samuel 17:16). They responded in terror (1 Samuel 17:11), even fleeing the battle line (1 Samuel 17:24).

But the Israelites remain at their camp. They talk amongst themselves about the imposing enemy. They also talk of the reward King Saul would give to any Israelite who could defeat the champion (1 Samuel 17:15). David, newly arrived from tending sheep in Bethlehem with food and greetings for his three eldest brothers (1 Samuel 17:14–18, 22), has seen the daily taunt. He has also asked about the reward to be given to the person who ends this shame. David questions who the Philistine is to defy the armies of the living God (1 Samuel 17:26).

The people who respond say "so shall it be," referring back to what the people were saying previously (1 Samuel 17:25). It was apparently common knowledge among the Israelites that Saul would give the man who killed Goliath great wealth. He would also offer his own daughter in marriage and freedom for the hero's extended family from taxation and obligation to serve the king. The reward was massive, in proportion to the massive threat.