When you are apprehensive about asking a question in a selling situation, just ask the prospect whether it is ok to ask. You will find that they always give you permission. You will also find that your reluctance to ask is most often not based in objective reality but in your own self-limiting beliefs or insecurity. If a question seems tough to you it is because it starts to infringe on what you believe is inappropriate. For example, many people are reluctant to ask about money. That is based on their belief that it is impolite or not socially acceptable or the fact that they are uncomfortable about discussing money in general or because they are not sure their product is worth that much or it seems like a lot of money to them. The list could go on and on. The sooner you recognize that you are the problem the sooner you can start to obliterate your beliefs by getting out of your comfort zone and seeing that what you were afraid would happens almost never happens. Your income will grow in proportion to the effort you put into getting out of your comfort zone.
