This passage seems at first to humorously show the extent of Wegg’s greed. Wegg is so protective of his mounds (which until very recently belonged to Boffin) that he resents Boffin even taking a single glass bottle from them. Wegg is even willing to use force to get the bottle back, suggesting the lengths he’ll go to. This shows Venus a dark side of Wegg and causes him to second-guess their plan. As it turns out, the glass bottle is indeed more than just a bottle and will play a role in the story later.