I charge $% for one name on each towel. It balances out with long and short names.
35 years ago it was $1 per 1 inch letter from the shop but they charged a minimum of $10 per item to cover set up costs.
Soozie . They supply the towel i charged $12-15, $2 for facewashers. Remember the time spent putting it all together, stabalizer & threads. If the query show them the door is my motto. :))
I do 3 initials or one name for $5 each. If the washer initials are small, may drop that price to 2 or 3 dollars. You may want to price what the local shops charge to give you some guide line.
At the store where I bought my machine, they always suggest $1.00 per thousand stitches. I never seem to get quite that much, but I've come close. It's going to take a lot more time and trouble if they want 4" letters rather than 2" letters. This pricing takes that into account. Some people set one price for last names or three initials and another lesser price for one letter. Remember, either way you have to stabilize and square everything up, and cover the towel over the top, even just for one little letter!