Get your taxes done using TurboTax

When reporting personal item sales, the amount of the IRS form 1099-K  (see here)

must equal the Proceeds for the sale reported on the IRS form 1099-B.  See here.

The cost basis within the IRS form 1099-B should reflect the actual cost.  

You may also report expenses by selecting I paid sales expenses that aren't included in the sale proceeds reported on the form at the screen Let us know if any of these situations apply to this sale.