I think something that's being forgotten is that we're used to the prices of things in today's economy. Let's look at flour (since it's a food staple that's been around at least as long as currency has) and the prices it's had in the US in the past 300-ish years:
In 2015 (today), the average price of flour in the US is $2.60 per 5 lbs.
In 1900, the average price of flour in the US was $0.12 per 5 lbs.
In 1800, the average price of flour in the US was $0.02 per 5 lbs.
In 1700, the average price of flour in the American Colonies was... uhh... 10 pence per 5 lbs... and since 12 pence equaled one shilling, and twenty shilling equaled one pound (currency)... uhh... someone else can do the math on that one.
So, I think the basic, 'raw' prices of standard things from NPC vendors would probably be... somewhat accurate to base the worth of gil on. Same with basic/low-level clothes bought from vendors.
HOWEVER, there's something else to consider that complicates and confuses things even more. We don't know the volume of what we're buying from an RP perspective. Mechanics-wise, the game requires just as many 4gil NPC units of sunset wheat flour for a Starlight Cake as it does for a Bowl of Raptor Stew. Meanwhile, anyone who cooks in the Real World knows that a cake as big as the Starlight Cake would require MUCH much more flour (several cups) than what would be needed to make a roux to thicken a single bowl of stew (a teaspoon or two). It's not just with the food, either. Mechanics say a cotton scarf (that little bandana-headgear that just covers the mouth) uses just as much cloth as a whole cotton acton, which is stuffed, quilted, and has multiple layers of the quilted/padded parts.... etc.
In 2015 (today), the average price of flour in the US is $2.60 per 5 lbs.
In 1900, the average price of flour in the US was $0.12 per 5 lbs.
In 1800, the average price of flour in the US was $0.02 per 5 lbs.
In 1700, the average price of flour in the American Colonies was... uhh... 10 pence per 5 lbs... and since 12 pence equaled one shilling, and twenty shilling equaled one pound (currency)... uhh... someone else can do the math on that one.
So, I think the basic, 'raw' prices of standard things from NPC vendors would probably be... somewhat accurate to base the worth of gil on. Same with basic/low-level clothes bought from vendors.
HOWEVER, there's something else to consider that complicates and confuses things even more. We don't know the volume of what we're buying from an RP perspective. Mechanics-wise, the game requires just as many 4gil NPC units of sunset wheat flour for a Starlight Cake as it does for a Bowl of Raptor Stew. Meanwhile, anyone who cooks in the Real World knows that a cake as big as the Starlight Cake would require MUCH much more flour (several cups) than what would be needed to make a roux to thicken a single bowl of stew (a teaspoon or two). It's not just with the food, either. Mechanics say a cotton scarf (that little bandana-headgear that just covers the mouth) uses just as much cloth as a whole cotton acton, which is stuffed, quilted, and has multiple layers of the quilted/padded parts.... etc.
