Albert Barnes Commentary 1 Kings 10:27

"And the king made silver to be in Jerusalem as stones, and cedars made he to be as the sycomore-trees that are in the lowland, for abundance." — 1 Kings 10:27 (ASV)

Made silver as stones - This strong hyperbole marks in the most striking way the great wealth and prosperity of the capital during Solomon’s reign. The lavish expenditure which impoverished the provinces, and produced, or helped to produce, the general discontent that led to the outbreak under Jeroboam, enriched the metropolis, which must have profited greatly by the residence of the court, the constant influx of wealthy strangers, and the periodic visits of all Israelites not hindered by some urgent reason at the great festivals.

The sycomore-trees in the vale (Shephelah) are also mentioned in 1 Chronicles 27:28. Like the olives and the vines, they were placed by David under a special overseer because of their value. The tree referred to seems to be the sycomore proper, or "fig-mulberry," which is still common in Palestine and is highly esteemed for both its fruit and its timber.