Right, so upon further reading, that 500cp/yr figure was for a laborer, soone who in modern terms would NOT be making 25-30 thousand USD annually, a more realistic figure would be 800sp a year to the modern 40-45 thousand USD a year, so you can think of a copper piece being about 3-5 USD.
For those wondering on conversions
100 CAD ~ 98 USD
100 BPD ~ 155 USD
100 EUR ~ 123 USD
100 AUD ~ 102 USD
So that figure of 600gp to 3.5million USD isn't accurate, it would actually be more like the 2 years earnings that CJ was talking about.
Subject: Wages and the value of coinage 
