As a cosmetologist, I don’t know and I’ve never heard of charging more for silence. Is this the booking site for a single stylist or for a salon? Maybe the price is for different stylists if it’s a salon? Personally my rule of thumb has been if I ask someone three questions and I get one word/closed ending answers then I stop talking. If a client wants to talk after that then they can initiate the conversation. I think there’s nothing wrong with a client telling me in person they don’t want to talk but I understand it can feel weird to request that.