Bid price depends on how much you're capable of yourself, how soon you want it completed, and inspection / reviews of his work elsewhere. I've hung sheetrock (using screws) and mudded it, no problem doing that. I can mud screw dimples and inside or outside corners, but I suck at flat joints. Like Turkey Creek, I'm too fussy and getting flat joints feathered out is not my strong suit. I hate sanding - a white powder nightmare - & a mess to clean up. I'll prime & paint all day long - it's the prep that sucks.
I'd pay $2K for that much drywall mudding / sanding. I'll hang the rock. I won't pay anyone to paint.