The ideal situation in business occurs when your client buys a product or service from you immediately with no questions asked. In the real world, almost any client has some concerns. If your product is fairly expensive, the concern may be in spending too much money. If it's inexpensive, the customer may think the product is cheaply made. This list could go on, but the picture remains the same.
Clients have concerns, and they have a right to have concerns.
Your objective is to deal with this quickly and make the sale. Behind the client's concerns is a need for additional information. Even seemingly stupid questions need to be answered politely, and just listening attentively might be enough to convince them of the sale. They just ask stupid questions, because they do not have all information you have. They also ask the same questions.