Registry Etiquette

Is there an etiquette as to how much items should cost on a registry? For example, should someone ask for a stroller that's extremely expensive if her family and friends can't afford something that expensive? I have a relative who is pregnant with baby number three and wants some expensive items that I know people in our family either can't afford or aren't going to purchase. I also know that many of them aren't going to go in together to buy the expensive items. Her older children are in elementary school and high school. Our family also feels that since she's already had two children, there is no need for her to have another baby shower. My grandmother has a theory: If you can't afford it for yourself, don't expect others to buy it for you.