1099K and deductions

I sold old (1900’s) Federal Reserve Notes in eBay and received the 1099K from PayPal. The Gross Sales amount was $8000. The face value of the notes were $7000. So I made a $1000 profit. I know that I need to show the $8000 of income on Schedule C. Where/How should I show the cost or Face Value of $7000?

 

Thanks