When it came time to drywall my 24x36, I hired a crew to do the ceiling (vaulted) because there was just no way I was going to try and do that myself. Just too high to work with 5/8" sheets, for me.
The crew I hired did the whole job (taped, two coats, ready for light texture) and supplied the drywall, for 800 bucks. This was about 936 square feet. They did the whole thing with 12' sheets. I think they had the drywall left over from a previous job, because the price was ridiculously cheap.
I did the walls (10') myself, and luckily, I scored 27, 12 foot sheets of 5/8" National Gypsum at my local Lowes for half off (which was $8.68 per sheet!), when they stopped carrying the 12 foot sheets of 5/8" at my local store.
They said they stopped carrying the 12 foot sheets of 5/8" due to the fact that new construction activity was so low.