Re the Form 1099 reporting to the IRS, some concepts above are being mixed together. The amount on the Form is not "income", it's only the total "gross proceeds from the sale(s)". To determine income (actually "gain"), you subtract your cost of the item. It's a lot like selling a share of stock or your house, the broker or escrow that closes the transaction reports to the IRS the gross proceeds from the transaction. It's then up to the taxpayer to report (generally on Schedule D, Capital Gains and Losses) both the proceeds and the cost of the asset sold, with only the excess of proceeds over cost being gain (income). So yes, you generally need to keep evidence of what you pay for items you sell.
If you are not in the "business" of selling (a muddy concept beyond what I can detail here), gains are taxable and losses are not deductible, but you may be able to offset losses against your gains ("see your tax advisor"). If you are in the "business" (probably rare for A-Gon), you get taxed on gains and deduct losses, and may be able to deduct losses against other income ("see your tax advisor"). Again, it's similar to selling stock through a broker or your house where an escrow agent closes the sale by processing payments and documents, and then reports gross proceeds to the IRS, and you have to figure out the gain, if any. Hope this helps.

