1 Kings 9:10 At the end of twenty years, during which Solomon built these two buildings—the temple of the Lord and the royal palace— 11 King Solomon gave twenty towns in Galilee to Hiram king of Tyre, because Hiram had supplied him with all the cedar and juniper and gold he wanted. 12 But when Hiram went from Tyre to see the towns that Solomon had given him, he was not pleased with them. 13 “What kind of towns are these you have given me, my brother?” he asked. And he called them the Land of Kabul,[d] a name they have to this day. 14 Now Hiram had sent to the king 120 talents[e] of gold.


d. 1 Kings 9:13 Kabul sounds like the Hebrew for good-for-nothing.
e, 1 Kings 9:14 That is, about 4 1/2 tons or about 4 metric tons

This is from God Vine.

Solomon gave Hiram twenty cities - It is very likely that Solomon did not give those cities to Hiram so that they should be annexed to his Tyrian dominions, but rather gave him the produce of them till the money was paid which he had advanced to Solomon for his buildings. It appears however that either Hiram did not accept them, or that having received the produce till he was paid, he then restored them to Solomon; for in the parallel place, 2 Chronicles 8:2, it is said, The cities which Hiram had restored to Solomon, Solomon built them, and caused the children of Israel to dwell there. Some think that they were heathen cities which Solomon had conquered, and therefore had a right to give them if he pleased, as they were not any part of the land given by promise to the Israelites.

The commentary at enduringword.com doesn't quite agree with God Vine's commentary.

King Solomon then gave Hiram twenty cities in the land of Galilee: This was not good. Hiram was indeed a friend to both David and Solomon, but the land of Israel was given to Israel by divine decree. Trading Israel’s land for a glorious temple and palace was not a good deal.

However, the transaction may be described here to show that Solomon was a shrewd dealer and got the better of Hiram in these arrangements. It seems that Solomon gave Hiram some fairly insignificant settlements and received a large amount of gold in return.

“To pay for the gold Solomon mortgaged twenty ‘settlements’ (rather than towns, for irim is used of any group of habitations from a hamlet to a metropolis).” (Wiseman)

“It is clear that Hiram considered the cities to be worthless, and taunted Solomon for giving him ‘good-for-nothing’ towns. Hiram nicknamed the cities Kabul, which literally means ‘good-for-nothing.’ Even though he was displeased with the trade, Hiram went ahead with it in good humor and sent Solomon 120 talents of gold” (Dilday). A talent is calculated to be about 70 pounds of gold. Dilday estimated the value of this gold at more than $50 million (something close to $161 million at 2015 prices).

But they did not please him: We don’t know exactly why Hiram was displeased with these cities. Perhaps he was displeased with his compromise, knowing that Solomon did something his father David never would.

This is from Biblehub.com.

Solomon gave Hiram twenty cities in the land of Galilee. These would most likely be in the extreme northern border of Galilee and so not remote from Hiram’s frontier. But they would be inland cities and no doubt, to a maritime people like the Tyrians, some territory along the seaboard would have been more acceptable. Josephus specially notes that the cities were not far from Tyre. The region in which they were situate was that called (Isaiah 9:1) ‘Galilee of the nations’ to indicate that the inhabitants were yet in heathendom. This might be a reason why Solomon chose them for his present to the Tyrian king.

This is from studylight.org.

Solomon gave Hiram twenty cities - It is very likely that Solomon did not give those cities to Hiram so that they should be annexed to his Tyrian dominions, but rather gave him the produce of them till the money was paid which he had advanced to Solomon for his buildings. It appears however that either Hiram did not accept them, or that having received the produce till he was paid, he then restored them to Solomon; for in the parallel place, 2 Chronicles 8:2, it is said, The cities which Hiram had restored to Solomon, Solomon built them, and caused the children of Israel to dwell there. Some think that they were heathen cities which Solomon had conquered, and therefore had a right to give them if he pleased, as they were not any part of the land given by promise to the Israelites.

Called them the land of Cabul - Whether this epithet was given to this land by Hiram as a mark of disapprobation, or what is its proper meaning, the learned are not agreed. That there was a country of this name in the promised land in the time of Joshua, is evident enough from Joshua 19:27, as it was one part of the boundary of the tribe of Asher; hence some interpret the word border or boundary, and so, the Septuagint understood it, for they have translated the Hebrew word ὁριον, which signifies the same. The margin gives another meaning.

Solomon used a lot of cedar and gold to build the Temple and his house. In past chapters the blackline drawings of the Temple and his house were on display. This looks like a financial document. The commentaries don't agree if this was a mortgage or a sale and return, but they do agree that the land was returned.