Many dreamers are attracted to the sales business. Unrealistic customer expectations should be identified from the beginning and explained to prospective clients. How profitable would it be to sell this product or solution to the market? What we want and what we can do are two different things. You can sell anything, depending on how many resources and how much energy you use to achieve your task. But is selling every item or service worth it? That is a different story altogether.
In my life, I have often had discussions with people who had absolutely no idea if something was feasible or not.