> Payroll taxes: OF COURSE they're saving the same amount on taxes!
No, they aren't, in the US.
> It's a % of what they pay you.
Not a flat percentage; the social security portion of payroll tax has an income cap (the smaller Medicare portion does not), which is less than what most programmers make, so payroll taxes do not go down proportional to income for workers who are above the cap to start with.