Unless, we want to consider a challenging quilt an investment in skill building. Most quilters feel challenged by the opportunity to do some custom quilting and hopefully more confident about it when it is finished. My earliest custom quilts included a lot of stitch in the ditch, and I felt more comfortable with it after each one. I think the same holds true for each new skill we try. I can't say “practice makes perfect” but time spent does improve the process and hopefully each time is faster/easier/better.
Even if the dollar per hour appears to be a loss, I’m going to challenge you to invest the time. Perhaps once a month, take on a new challenge. Make yourself learn how to do something new.
In the end, you’ll gain confidence, not only in using a new skill, but the reputation for a new level of work, and finally, the confidence to charge what that new skill is worth.