"Average skill labor" would not account for a reasonable comparison in standards of living. It takes the exact same amount of "average skill labor" to perform a string quartet in 2020 as it did in 1720, but the cost today is far higher than it was back then, if assessed via a reasonable consumption basket (perhaps involving chained comparisons over time, etc.). That's no coincidence, of course; performing a string quartet is the rare case of a good/service that has not been made cheaper by technological progress and growth.
Comparing by food prices, while ultimately a bit more reasonable, would plausibly err in the other direction since food prices have radically fallen in modern times. It's very helpful to expand the basket beyond food, and additional historical data helps take a guess at questions like "how much would good X have been valued in Roman times, if it was available on the market?"
Comparing by food prices, while ultimately a bit more reasonable, would plausibly err in the other direction since food prices have radically fallen in modern times. It's very helpful to expand the basket beyond food, and additional historical data helps take a guess at questions like "how much would good X have been valued in Roman times, if it was available on the market?"