dummy,
Do I assume you're going with a smooth finish inside and a broom finish outside?
Around here, the prices vary a bit based on your requirements.
I've gotten work done for as low as $0.60/sq ft. (driveway) and up to $1.50 depending on what needs done.
A couple things to consider (and the finishers may take into account when they give pricing):
How much time can you give them to do the project? A continuous pour may cost more than allowing sections.
Do they have floor drains or other things they'll need to work with? With the floor drains, it normally takes a little more effort to get correct sloping.
How are you going to sectionalize the concrete for expansion (zip-strip, saw it in later, expansion joint, or whatever it's called when they use the thing that looks like an edger but goes up the middle of the crete).
How close can they get the concrete truck? Wheelbarrowing adds a little premium.
The way in which the finisher is going to do the work will change things. If using a power screed and troweler the price will probably be different than if doing by hand.
For the concrete itself:
At least around here, if you're doing it on a weekend, price goes up $10/yard for concrete.
Have you considered getting fiber in the concrete. I've seen a couple finishers really mess up the wire whereby when done, it didn't do anything. (they walked on it so much they pushed it back down).
Ask the finisher who's going to order the concrete and release the trucks. If he is, see if there's a premuim. Some people aren't very nice and throw 5-10% on top of the price.
Don't forget to get a good sealant for it. Some finishers will do this for free. If they won't, it's an easy job. Just have good air circulation.
Do you have stone under the vapor barrier?
Watch the weather. To save cost, try to schedule when it's warm enough where they don't have to add calcium or other retardant.
