EBay, Collectors, Flea Market & Antiques

According to ebay;

"Only goods that are sold for a profit are considered taxable, so you won’t owe any taxes on something you sell for less than what you paid for it. For example, if you bought a bike for $1,000 a few years ago, and then sold it on eBay today for $700, that $700 you made generally would not be subject to income tax."

IRS: Fine, just show me your receipt for that bicycle that shows you paid $1000. Oh wait, you don't have one because you bought it in 2002 and don't have it? Too bad.

Please pay the income tax on the $700 then, since you have no documentation.