Being a longarm Quilter here’s my take- I Never expect a tip.
There have been times when a customer was very pleased and added a bit more to the bill, or when I did a rush job they showed their appreciation. One time I had someone say.....” I’m paying you more- it is so worth it, you don’t charge enough!”
all of this is very appreciated but never expected. Like you stated- it’s not cheap to have your quilt longarm quilted. If you feel that a little extra is warranted then by all means- give that tip. But don’t feel obligated. It’s not like a waitress working for $2.85 an hour and depending on tips. ( and yes, that is the normal pay for a waitress in Michigan)