You could google prices hand quilted quilts and there will be stuff come up. The one group I quilt w/ charges by the foot of thread. I couldn't keep track of that, too difficult....
Personally, I enjoy the handquilting, so doing it for others is a way for me to get my "fix", and someone gets a treasure. I just finished a bit smaller than a twin size coverlet that was about 25% done when I got it and got $100 for it. But, the woman was also a senior citizen on a limited income. Her mom had started the quilt years ago and the joy, appreciation, and total gratitude was 10 times more worth the dollars that she gave me.
You'll never get your time paid for, but have fun!