A few years ago, before I started doing any leatherwork and way before I ever bought a sewing machine, I had a belt re-sewn. The length was 12inches and 1 & 1/2inches wide. So for 2feet 3 inches, I was charged $30.00AUD. That was a lot cheaper than buying a new belt for $75.00AUD. I was ok with paying more than $1.00AUD per inch, so I find your question irrelevant, unless you pose your question to people in your country and also within the economic region as most of your customers.
If you charge $1.00 per inch, I am guessing you would get no work. On the other hand, if the repairman in Australia was to charge 17cents per inch ($4.59 for the job I had done), he would not be able to pay his bills.