I own a salon. We spend over $2500 a month on nail supplies that we USE on clients (gel polish) is this an expense, or COG since we use the product to sell a service?

Is it better to have a higher COG or salon supply expense. We use 90% of our inventory on our clients. since we pay taxes on our services.... is this better to add the supplies we use to do these services as an expense or COG?