We've been doing small repairs for some time now and is a real niche market as most carpet fitters cant be bothered and lots of cleaners dont know how.
We use a cookie cutter for most cigarette burns and its really effective, once you've praticed a bit first, theres not much to it, but you do have to qualify a few things first, i.e. do they have spare carpet that matches well, " it may not look perfect" etc.
We charge around £40 per repair and takes about 15 - 20 minutes.
We've never had a complaint yet, but i would say it works best on dense tufted carpet rather low profile or looped.
steve