Don't forget the CPF is only applicable up to $5000 or so, so the rest of your savings could be saved elsewhere...
CPF deduction is on first $4500 on your pay slip (used to be $5000) and 20% that comes from employee's pay is only $990...
For example :
If your income is $5,000 per month...
Your CPF contribution will be $990
Your take home salary would be $4010
If your income is $10,000 per month...
Your CPF contribution will still be $990
Your take home salary would be $9010