I'm sorry for your uncomfortable experiences. Anyone who does not quilt, does not have any idea of what it actually costs to make a quilt. A friend of mine had a very bad experience with a mutual friend. She had asked her to make a quilt for her granddaughter and specified penguin fabric. It took time to locate the fabric, and it was more than she expected to pay, however, she made the quilt and when she gave it to our mutual friend, she thought it had taken too much time and said she didn't expect to pay that much. My friend told her to give her what she thought was reasonable, which unfortunately only covered half the cost of materials. It's hard when making things for friends and family, as many expect it as a gift. Right now I have been "commissioned" to make a queen size quilt for a friend and she would like me to use the colors in the painting Starry, Starry Night, by Van Gogh (I think-Sr. moment); but we worked out a barter system. She was moving and her daughter was leaving some of her Barbie Dolls plus an American Girl doll with some furniture, wardrobe, cradle, which I believe were hand made, the doll, a beautiful brass bed with beautiful bedding, the doll and accessories. Her daughter took very good care of her things, so I think I may have gotten the better deal. Our DGD Zoe is 5 and I can't wait to see her face when we give her the doll and some of the accessories - oh, plus she also had a wrought iron old fashioned school desk. In this case, my friend, who also sews, had a good idea of what was involved and was even going to pay me more; however, I think we got a mutual good deal. Now I just have to figure out what to make, but I know my DGD will be excited at Christmas, plus I feel as if we are giving her items we could never have afforded if we had paid full price.
I'm afraid I went round about in an answer, but if someone asks you to make a quilt, I would tell them the approximate cost of all the materials, plus some payment of your time and get a down payment for the cost of fabric. If they don't like the price, you won't have to make them a quilt and stand firm.