Just going through this at the moment and am happily paying $1700 to get my 6mx10.8mx2.4 shed put up. So far, walls and frame up after 1 day and the rest will be finished today (roof with aircell, roller door, 3 windows and 1 PA door). Pretty happy with the work so far, hoping the finished product is up to scratch. $1700 for 2 blokes over 2 days seems like a fair price.
For me, just haven't got the time or experience to put it up myself. Biggest problem/difficultly I've heard is making sure the frame is perfectly square. If I was to DIY i'd arm myself with lots of photos of an existing shed as a reference. Another reason for getting the pro's in is that the beams are heavy and potentially dangerous for us amateur builders. Wouldn't want one falling on my mates, missus, kids, myself etc while putting it up.