i do kitchen knives, and so i sharpen and regrind a lot of cheaper kitchen knives... but 400 grit belt and buff and done on the grinder, the edge i finalise on stones... not matching the crappy factory finish... It is part of making a customer's existing knives useful... it means they can use the knife i made for what it was designed for, not for whatever, because it was the sharpest... it almost never means less sales...
i have an arrangement with other chef knifemakers, ok there are only 5-ish real, established chefknifemakers over here, and they are all stand up people, living far from me, that their local customers can bring me their knives to sharpen and do minor chip repairs... for free. we have horrendous post office turnaround times.... and couriers cost quite a bit.
I have, in secret, fixed a friday night late before the show kichen knife grind when another kitchen knife maker was having a really tough personal time, and the client, who is also a client of mine, asked for a favour. I think we all make mistakes, especially when new... and if i was to have a serious personal crisis where a customer might get a delay in service from me, i would like to know a friend who is a maker would help out, if he was confident to do so... and not do it, if he wasn"t confident to do so...
Then there were the corrections i made to knives that were from newer makers, who perhaps don"t know what to aim for... these were all users... and kitchen knives... and i usually ended up having conversations at shows with them or one of my clients bring the newer maker over for q&a and i highlight geometry issues they can work on, and we fix a grind together... or just compare various geometry options, i usually feel that this person's work is worth fixing, and would be a good maker to add to the ranks... he has the feel for kitchen knives... so help him shrug off less than ideal earlier work, faster.
I won't touch a major repair or rework on another maker whose work is at or above my level ito geometry and fit and finish... i can't see that being a good thing for anyone involved.
I don't work on makers who do kitchen knives or razors for a lark... I can't do minor corrections on those, matching their usual work... it would still not be a kitchen knife...