Yes, you realize first hand when you go into biz on your own, and have to pay yourself on payroll.
Basically DOUBLE your SS and Medicare withholdling tax and add in a few local/state taxes on top that the employer usually pays. Then pay full insurance premiums on top of that, instead of partial amounts.
I thought at first I might make double my earlier employee income, but it's turning out about 50% more at best, but now having to manage all the quoting, PO's, invoicing, accounting, blah, blah, blah.