USA How to post goods purchase/sale for promotional purposes

[Mnow1]

Business owner wants to purchase goods for resale to new customer at cost so that new customer can try out the goods with his customers effectively making no profit to Business owner. Business owner doesn’t want to post as COS and revenue to that particular product because it will bring the average gross profit down for that product. Would it be appropriate to post the purchase as a promotional cost instead of COS and the revenue as other or promotional revenue?