Albert Barnes Commentary Revelation 18:19

"And they cast dust on their heads, and cried, weeping and mourning, saying, Woe, woe, the great city, wherein all that had their ships in the sea were made rich by reason of her costliness! for in one hour is she made desolate." — Revelation 18:19 (ASV)

And they cast dust on their heads. A common sign of lamentation and mourning among Eastern peoples. See Barnes on Job 2:12.

By reason of her costliness. The word rendered costliness—timiothv—means, properly, preciousness, costliness; then magnificence, costly merchandise. The luxury of a great city enriches many individuals, however much it may impoverish itself.

For in one hour is she made desolate. So it seemed to them. See Barnes on Revelation 18:17.