You did a great job with that one. The border is perfect for it.
I think trying to make something from what someone else has started is frequently more difficult to do than a start from the beginning project.
If you remember how much time you spent on that quilt- including planning/thinking about what to do with the blocks, shopping and fabric prep time, and actual "doing" time - multiply that by what you think is a reasonable cost per hour.
Remember, you are SKILLED labor. (plumber, electrician, mechanic - - - - )
Than add in your actual out-of-pocket expenses.
That might give you an guesstimate for what to ask for next time. (Be prepared to shock yourself with what you come up with.) Than be prepared to deal with what your market might bear.