I have wondered the same thing myself - a recent experience I just had made be go and look on Etsy to see what custom made quilts sold for. Hmmmm
I just made a king size quilt for a friend of a family member. She saw the quilts I had made for my family member and really like them. She said she would pay me to make her one. We didn't discuss how much, but I did explain how much time it took to cut the fabric, piece it together, quilt it and bind it. Also, before I started I had her pick a pattern. and told her how much the material would cost if she used quilt shop quality fabric. That was about $300 just for the fabric, plus batting. I also told her it would cost over $140 to have someone quilt it if she wanted it done professionally as I am a beginner on my mid arm. Of course she wanted me to quilt it. I also made pillowcases to match, at her request. Before I purchased anything for the quilt I would get her approval first on the cost. When it was finished she just gave me the money to cover the cost of all the materials - Nothing else. I was shocked since she said she would pay me to make it for her - I would have been happy with just $50 . Perhaps when she said that she would pay me, she only meant for the material? I didn't get that impression. But I didn't expect $0 for my labor. I must say also that it was difficult for me to make a quilt for someone I didn't know. I didn't like the pattern they picked or the material. So, I didn't get as much enjoyment out of it as when I make one where I selected the pattern and fabric and knowing the tastes of the person I am making it for. Lesson learned!!! It was my own fault for not speaking up in the beginning. I just know I wouldn't ask someone I don't really know to do something for me and not give them anything for their time. I never expected a lot - I know people don't realize the labor that goes into quilts. So, I told myself just enjoy the fact that someone has a nice quilt to enjoy that otherwise would not have been able to have one. I recently retired, so I will just consider it a gift of my time, but learn from it.
I have only made quilts for my family members and of course those were given as gifts of love. I have only been quilting for about 4 years and I haven't run out of family members yet!. I have yet to make one for myself - like the cobblers kids have no shoes, this quilter has no quilts LOL. I keep putting mine off because of the joy I get from giving!