re: Cost of pouring concrete for patio

600sqft at 4" with a 8" deep by 6" wide will get you to need about 9 cuyd's which roughly will cost $900 give or take.

figure $100 for formwork
figure $250 for rebar
figure $700 for labor
figure $160 for tax

looks like $2100 plus or minus a couple hundred
this is assuming you set set the forms and rebar
if not add another $300
also, put a little bit of expansion pad if butting up to other existing concrete.
and have the place and finish guys sawcut a couple of control joints every 8x12 (or any variation but not to exceed 13' an any way) area to control cracking