scammers!

working for other people is a scam.
it seems that i had to set myself up with an umbrella company as i am a contractor. the umbrella company issues an invoice to the client, for my pay. by the time the money actually gets to me, i receive half of what was on the invoice. HALF!? how the fresh hell is this possible?
taxes, taxes, admin, more taxes and then i'm left with a wee amount.