Most accountants/bookkeeper will have nil or very low costs of sales as tend not to have costs that vary in relation to fees generated.
For myself personally all my costs are overheads eg IT costs, rent, telephone, advertising etc but at the end of the day doesnt really matter if you classify as cost of sale or overhead as the important figures in the p&l are what the sales are and what the bottom line proft is. Everything in between is just classification.
Its not like we are buying in goods and selling them on therefore need to keep an eye on gross profit and GP% like a shop/restaurant etc.