Technically you are suppose to claim any and all income you make selling stuff on ebay. Even the occasional used pair of boots should be claimed.
But, if you claim it as income, then you are also allowed to deduct the cost of depreciation. That is why the IRS doesn't care about not reporting casual sales. If you clean out the garage and sell a bunch of used items, by IRS standards you will be losing money cause you selling everything for less than you paid for it. But if you buy a wrecked car and sell the parts for more than you paid, including selling expenses, then you have just made taxable income that you are required to report.