Did David pay fifty shekels of silver or six hundred shekels of gold for the threshing floor?

The two books price two different things. Samuel records what David bought on the spot for the sacrifice: “the threshingfloor and the oxen” (2 Samuel 24:24), with, Gill adds, the threshing sledges and yokes that Araunah had offered for fuel (24:22). That cost fifty shekels of silver. Chronicles says David paid six hundred shekels of gold ‘for the place’ (Hebrew bammaqom), and goes straight on to say why the site mattered: David declared it the place for the house of the Lord (1 Chronicles 22:1), and Solomon later built the temple there, on Mount Moriah (2 Chronicles 3:1). The temple and its courts needed far more ground than a threshing floor, so the larger sum fits the purchase of the whole property. John Gill gives this explanation from the Talmud: one purchase, of the floor and oxen, for silver, and another, of ‘the place’, for gold.

A copyist’s slip

Keil and Delitzsch thought that one of the figures had been miscopied, probably Samuel’s, since fifty shekels of silver seemed too low for the site when Abraham had paid four hundred shekels for a burial plot (Genesis 23:16).

Fifty from each tribe

A Jewish suggestion, reported and rejected by Gill, was that fifty shekels were raised from each of the twelve tribes, making six hundred.

Chronicles does not say in so many words that the gold bought more land; that is inferred from ‘the place’ and from what follows in 1 Chronicles 22:1.