Charles Ellicott 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)

Alas! alas! that great city . . .—The lament is parallel with the laments of the kings and the merchants; the difference is the appropriate reference to the destruction of the shipping interests. Woe! woe! (or, Alas! alas!) the great city, in which all who had their vessels on the sea grew rich out of her costliness.

By her “costliness” we are to understand her extravagances of living, and the splendour of her palaces which drew materials from all ports of the world. The lament ends with the repeated cry, “in one hour.” Because in one hour she was desolated.