Given that the gold price has increased by a factor of 8 in the last 20 years it's hard to see how that could be true. Even if it happens that there's an equivalence between today and 1450, a shoemaker in 2000 would be earning 8 times more.

EDIT: To put it another way, over the last 20 years the Dollar, Euro and Pound have all approximately averaged out to their target 2% inflation rate. Prices in gold terms have averaged to 9% deflation per year. Since 9 > 2, gold is less stable than modern fiat currencies.