I would take a look at this link: https://wow.gamepedia.com/Money
Typically, the way I RP, a handful of copper can feed a peasant family of 4 for a day, though it wouldn’t be your best quality stuff.
For sake of our argument, let’s say it takes 5c to feed the hypothetical family of 4 (as per the link, vegetables cost 1c, so 5c should be a day’s worth of peasant food), we can multiply this by 3 to account for living costs, housing, clothes budget, etc. etc. winding our total to monthly living expenses to ~4s 50c for the poorest of the poor. Barely minimum wage.
The average wages of a peasant would be somewhere along these lines, with a generous salary being greater than 4s 50c and a bad salary being less than this number.
Copper would be the primary currency used by the “lower” class. They probably view 1s as a lot of money, with 1g being an impossible pipe dream.
The middle class probably uses a mix of copper and silver on a daily basis, with 1g being a lot of money.
Upper class probably treats copper like pennies, not worth picking up from the curbside. Most likely their daily spending money is silver, but gold isn’t really all that hard to come by. Probably got loads of it stowed away somewhere.
Now, government spending (such as the listed prices for units), are probably accurate to a degree, but you have to remember that these prices are inflated via good old bureaucracy. What the average citizen spends copper or silver for likely costs gold for the government.
EDIT:
Living Expenses:
I’ve gone ahead and written down my own personal take on the living expenses of the social classes. These are just living expenses, not taking into account spending such as educational or impulse buys. For calculation, I’m going to use the good old family of 4 assumption, with the below (entirely speculative) values. I think given the above they are fair estimates.
Again, these are living expenses, not salaries.
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Really Cheap Meal: 5c/day
Really Cheap Living Costs: 10c/day
Total: 4s 50c/month
Yearly Total: 54s 0c/year
-
Cheap Meal: 10c/day (doubled due to the addition of cheap beers vs water)
Cheap Living Costs: 15c/day
Total: 7s 50c/month
Yearly Total: 90s 0c/year
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Lower Middle Meal: 15c/day
Lower Middle Living Costs: 20c/day
Total: 10s 50c/month
Yearly Total: 1g 26s 0c/year
-
Middle Meal: 17c/day (starting to slow down)
Middle Living Costs: 25c/day
Total: 12s 60c/month
Yearly Total: 1g 51s 20c/year
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Upper Middle Meal: 20c/day
Upper Middle Living Costs: 30c/day
Total: 15s 0c
Yearly Total: 1g 80s 0c/year
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Upper Class Meal: 1s (imports, fancy cooks)/day
Upper Class Living Cost: 10s/day (housing costs spike upwards, salary for servants)
Total: 3g 30s/month
Yearly Total: 39g 60s/year
For upper class going forward, I’d add 10s for more searvants/bigger houses (iterative, of course), and I’d multiply it by 10 if said upper class has a lot of land/castle. I’ll crunch an example “Aristocracy” living cost.
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Aristocracy Meal: 2s/day
Aristocracy Living Costs (Med. Castle): 2g/day
Total: 60g 60s/month
Yearly Total: 727g 20s/year
For wages, a good wage would be higher than cost of living, bad lower, and wage slave would hover around it.
These are just some of my personal thoughts on the matter, definitely not a “hard rule” or anything else, just my own interpretations of things with some basic math thrown in. Take it with a grain of salt and not everyone is guaranteed to share these opinions.