Let’s imagine a world where time machines are invented.
Hypothetically, what’s stopping anyone from travelling to the past, where the dollar is much more valuable, and buying things at a much lower price? What if you then go back to the present, sell those things at a higher price and repeat the cycle? And wtf would happen if everyone there started doing that?
If I steal a gold coin from the year 2000, then, with that coin in hand, travel to 1999 and steal the same coin, I now have two copies. I then travel to 1998, 1997, et cetera, et cetera, on down the line, each time I gain an additional copy of the same coin. I then take all these coins with me to the present and spend them. Now just swap out the years for 2 minute intervals and you’ve got an infinite number of coins, or nearly so, anyway.