Does your client creates fragrances? So they buys other fragrances to use as raw materials in make their own fragrances? Or do they just buy fragrances and resell them as-is?
If the latter, I do not believe there is an COGS involved at all, just Expenses. (Though check with your Accountant on the latest tax laws.)
I believe you would only use a COGS ACCT if you make something out of raw materials. If you make tables, the wood is COGS. But the tools, work space, shipping, etc. are all Expenses. Even if your client took the fragrances and put them in new bottles with their logo, that's not COGS in my opinion, also just Expenses. But I'm NOT a Tax Accountant.