“no lack of gain.” The Hebrew word translated “gain” is shalal (#07998 שָׁלָל), and it means spoil (as in the spoils of war), plunder, booty, prey. It refers to the spoils or booty won in war. There are some lexicons that claim that the word should simply be “gain” in this verse, but there does not seem to be good lexical support for that; it seems clear that “gain” refers to the gain she won in the daily wars of life.
The picture being painted in the Hebrew text in Proverbs 31:11 is the husband having the riches he needs to be peaceful and comfortable because his wife goes out and fights the battles in life necessary to procure a living, and brings the spoils or plunder she has won back to the household. This is one of the verses in Proverbs 31 that shows us that the wise wife of Proverbs 31 refers to both men and women, just as Lady Wisdom and Lady Folly throughout Proverbs refer to both men and women (other verses that are typically male behavior are Prov. 31:16-17).
Women would not typically be portrayed as going out of the house into the world and fighting the wars of life that brought prosperity to the household. It was the common cultural understanding that the women’s domain was inside the walls of the house while the man’s domain was outside the house. Going and fighting the worldly wars that brought success to the household was the job of the man of the house, and the wise man fights and wins those wars for his family and brings home the spoils of war. [For more on the woman in Proverbs 31 referring to both men and women, see commentary on Prov. 31:10].