After Imhotep has died — with the sequel-setting-up line "Death is only the beginning" — Beni accidentally triggers the destruction of the city of Hamunaptra when he rests a heavy bag of treasure on a booby-trapped lever. He and Rick, Evelyn, and Jonathan run to escape as the doors and ceilings start closing from above.
We already know Beni is only interested in self-preservation and wealth. That greed literally triggered the event that leads to his death. And even as the city is falling above him, he continues to drag the sack of treasure, which slows him down until he's forced to abandon it to escape through a closing door. Beni catches up to the others but is seconds too late to follow them to safety through another closing doorway. If he'd left the treasure behind from the start, he may have made it in time. Beni is trapped in a room full of gold, a pretty heavy-handed visual cue that even the most valuable treasure isn't worth your life. And then he's eaten by scarab beetles.
However, Beni isn't the only treasure lover in The Mummy. The only reason Jonathan is interested in Hamunaptra is because it's rumored to be the place where the Pharaohs hid their treasure. But the difference between Jonathan and Beni is that Jonathan isn't entirely selfish. Beni is willing to abandon friends and lure them to their deaths to save himself, whereas Jonathan risks his life to save Evelyn. And in turn, when Jonathan is tempted by the treasure room on their way out of Hamunaptra, Rick and Evelyn pull him away to safety. Another direct comparison: when Jonathan encounters a scarab beetle, Rick saves his life by cutting it out. In the end, friends are the real treasure.
