So the easiest way to figure out how to price a quilt is to make a square mini-quilt, and use that to get an idea of a base price-per-unit for your work. I made a 20x20 doll quilt and cost of materials and labor put the price at $50, so now I know the absolute floor for a finished quilt is $25 per 10" square.
After that, I personally have a tiered pricing system based on what a person wants.
Tier 1- Don't care what it looks like or when you get it? Then it's a gift and free.
Tier 2- Choice of color way, size, and simple pattern- $10-15 per 10"
Tier 3- Total input on fabric selection and pattern- $25+
Since quilting is my hobby, I don't my factoring my desire to do it anyway into pricing for people if they're flexible about what they get. I think since you took this project on out of personal interest, it's not unreasonable to offer a deal or even make it a gift if you feel that's an acceptable outcome. Just don't hesitate that you did this for you if this person or anyone else comes around expecting free quilting.