Repair prices really depend on where you are and how many other squires are in the area, as well as how long you’ve been in an particular place.
If you’re set up in a player town, odds are you’ll have to sell at close to zero profit (115 silver per repair kit is zero profit) If you’re set up outside a dungeon or hunting grounds, you can probably get away with charging for more since you’re providing extra convenience, but also losing potential sales due to less foot traffic in the area.
I’ve had an established repair shop in Orsha on the Klaipeda server for a while, so I get plenty of customers even though there is another repair shop that’s 1 level higher and always just undercuts my prices. Customer loyalty seems to be a thing. I sell out of materials at least twice a week, which nets me somewhere around 350k silver in profit (I buy 32,000 materials when I restock).