If we restrict this to people working in high demand engineer/software related fields, then I would say

#1,3,4,5,6,7,9,11 add up to at most 30%

And #2,#8,#12,#13 could be worth 10%. I don’t think #10 is a guaranteed benefit, and usually is in exchange for forgoing any other grievances you might have against employer.

But that would be restricting it to highly paid, in demand professions. For other people (upwards of 80% of the US), many of the items on that list don’t apply to them, so I don’t see how it would cost 40% more for an employee versus contractor.