Yet another approach (one which I am still working on) allows you to break 
Wealth up into its compnoent parts: Starting Cash and Inherent Wealth. 
Inherent Wealth is defined by what kind of income you can get, and how hard 
you have to work to make money. With this approach, use the following charts
 
Starting Wealth    Cash      Cost
Dead Broke         x 0       -15
Poor               x 1/5      -9
Struggling         x 1/2      -6
Average            x 1         0
Comfortable        x 2         6
Wealthy            x 5        12
Very Wealthy       x 20       18
Filthy Rich        x 100      30
Multimillionaire   x (x 10)  +15

Inherent Wealth    Workweek  Cost  Free Status
Dead Broke          0 hours  -10    0
Poor               50 hours   -6    0
Struggling         40 hours   -4    0
Average            40 hours    0    0
Comfortable        40 hours    4    0
Wealthy            20 hours    8    1
Very Wealthy       10 hours   12    1
Filthy Rich        10 hours   20    1
Multimillionaire   10 hours  +10   +1