Check it -
Central Texas Metal BuildingCliff Notes version:
Concrete - $5.45/sq.ft. - this may be on the higher end, but it was also the best guy in the business. (don't cheap out on the foundation)
Pad work before concrete (had a couple feet fall across pad, brought in crusher fines): $1.25/sq.ft. however I believe this was a function of how out of level the natural ground was, not actually the sq.ft.
Building - I used Mueller. Still undecided on it. A well seasoned home and commercial builder I bounce ideas off said "If I'm going to live in it (bardominium) - Mueller bolt up. If its a shop/storage - independent builder weld-up". The more I ponder this, the more I think he is right. I can go into more detail if you'd like.
Muller - I would rate their quality fair or acceptable to good. Very good does not come to mind. Also take their "contractors" list with a grain of salt. I ended up using a sheeting guy through them, mistake. Again, quality was fair or acceptable.
I just went through everything you're about to. Let me know if I can help in any way.
Edit: Found my sheet of weld-up quotes. $3.5-$4 / sq.ft LABOR to erect a building. Can budget $18-$22/sq.ft. to "get a building up" (concrete, steel, labor, sheets)