[swarmee]

You probably should ask an accountant.

But... before 2018, it was routinely accepted that "hobbyists" with sales could subtract the expenses incurred (original cost of item, fees, shipping, etc) and then were only expected to self-report and pay Federal income taxes on their profit margin.

That changed in 2018 with the passage of the new tax law that doubled the standard deduction. Hobbyists now owe taxes on their entire sales prices, while businesses can still subtract deductions. PayPal will send the IRS a 1099 if you have transactions (goods) of over $20,000 in sales and 200 transactions. They might send it anyways. Just because you and the IRS are not sent a 1099 does not mean that you don't owe taxes. Just because you sell through a consignor doesn't mean that you don't owe taxes. You do. You may want to register as an LLC to qualify as a business.
But please confirm with an accountant.

Edit: You may be able to debit cost of goods sold if you report the sale as a Collectible investment, rather than ordinary income.