It also depends to some degree on the local job market, average rates of pay for comparable or even dissimilar work.
For example, here in N. California/Silicon Valley, the rate of pay would likely be higher than a lot of places, just to offset the high cost of living.
Here a 1 bdrm apartment is $1400-1500 a month, gasoline prices are high, insurance is more expensive, utilities are some of the most expensive in the U.S., a business license for a sole operator is $235 a year, property taxes are 1.25% year, sales taxes are up close to 10% in most communities, and the state takes 10% income tax and still manages to end up buried in debt.
Average income is over $50,000 year, household income is over $75,000. A Starbucks employee makes about $30,000 yr. A bus or garbage truck driver with a little experience makes $75,000 a year. A cop or fireman starts close to $90,000 and goes up to $125,000 or more. Meanwhile an engineering position at Google starts at $35,000, but has a ton of perks including stock options, ample opportunities for advancement... and they just announced a company-wide 10% pay increase.
An in-house photographer position (at a well established commercial studio) that was advertised here not too long ago here offered around $50,000 year for someone with reasonable experience, with typical benefits. By comparison, the Smithsonian was advertising for a Director of Photography earlier this year, requiring a ton of experience and education, and offering about $55,000 year plus typical benefits, if memory serves.