Presenters will have 2 people talking in their ear. Director and Producer.
The director will tell them what camera they are cutting to next, tellthe presenter when they are in vision, as well as telling the presenter when they will be running a piece of VT.
The producer will be the one who says about the prices, and when the presenter is running out of things to say, or important things they need to point out, they will tell them. When Peter Simon has his 10 minute speel, I'd imagine that the producer will give him something to talk about. E.g. the producer may say "How rare is tanzanite" and then the presenter will say "Tanzanite is a very rare stone...." And Peter can go on for hours! :L The producer will also be the one saying how many are on the phones Etc.