Get your taxes done using TurboTax

It seems you did not enter the cost. See the information below and review the 1099-K entry to be sure you entered your cost, which is the same as the income if personal use item sold at a loss.

Personal Items Sold at a Loss.

The costs associated with the sale of personal items can be used to offset the income from those items.  If these times were sold at a loss, you can simply track this information and keep it with your tax return (you need this in any event) without reporting it.  Otherwise you report the income and cost at the same amount because a loss is not allowed for this transaction.

Personal Items Sold at a Gain.

One personal item or a group of personal items sold in one transaction or many that results in a gain requires the gain to be taxed. 

It's not necessary to enter each individual sale as long as you have the detail to show how you arrived at your return data.