what good are the pearls after buying every thing at mamagos??? who else uses them for cash???

If I remember correctly they aren't good for anything after that. However collecting all of the pearls is the only way to get the mini-game disk (I think the game is called Pearls???) from the Rhino brothers. The game is something else. So simple yet so frustrating. Playing the mini-game disk increases your score on the most wanted list.