You have $30,000 in sales, not profits. The profit is what's taxable. Have you actually calculated the profit?
Is this your first year as an ebay seller? If not, how did you report it in the past?
If you are selling personal items you may not deduct losses, regardless of which method you use to report the income. For example, you sell a used book for $10, that you paid $30 for and a collectable vinyl record for $50 that you paid $5 for: you have $45 of taxable income (50-5) not $25 (50 -5 + 10 -30).
