A visitor has picked a car and wants to call, but there is no phone number anywhere
What it costs the business. A buyer who has reached the "I'm coming to see it" stage looks for the dealership's number. If they can't find it, they won't fill in a form and wait for a reply; they will go back to search and call another dealership. For a car dealership this is the most expensive loss: it is not just a lost visit, it is a customer who was already ready to buy.
What we do. We put the number in the header of every page and make it tappable, so that on a phone the call starts with a single touch. About an hour of work.