One of the eminently attackable facets of that claim is the varying availability of goods over the millennia, making it impossible to have a really stable and precise measure of value against which to measure gold's purchasing power. You can't buy silphium or Roman concrete today for any price, for example, nor a ticket to a gladiatorial match, and, from a certain point of view, most of the functions fulfilled by handmade Roman togas are today fulfilled by mass-produced machine-stitched US$200 wool suits, or even a cheap sports coat, jeans, and T-shirt. And no amount of gold would have bought you penicillin 100 years ago, much less in Roman times.
Sure, and the greatest thing about modernity is that during the Roman Empire you would have been executed for wearing Tyrian purple, while now anyone who cares to spend the money is entitled.
Despite Sumptuary law's then it was often the case, as it is now, that anyone who cared to spend the money could become a magistrate and wear a stripe of purple, or spend more money to overthrow a ruler and replace them .. going full purple.
Wearing purple signified not only that you could afford purple, it also signified you could bribe censors to allow you to wear purple.
Much like having the latest model of a limited edition sports car today; not only can you afford the car but you can also afford enough shittier models to be moved up the preferred buyer list or otherwise bribe the sales reps.
