At what point do you files Pokemon Income tax? lol

Let's say you bought 100k worth of pokemon cards from various sources (in person offerup, fb, card shows, ebay, tcgplayer, etc) and sell it at a later date for 100k (100%) profit, how do you even report that to the IRS? Whose to say you can't just make up numbers and say you paid 190k and net gain was only 10k even if you sell all online? (ignore ebay cut, shipping, etc for sake of simplicity)