I used Mueller Metal Buildings for my smaller building. And they did a great job. Made a couple mistakes on the custom frame pieces, but quickly corrected those. They are primarily a Texas based company, with a few locations in OK and LA. Maybe something similar closer to you. They have standard buildings, or will custom design whatever you want. I basically chose a standard building, but customized it by changing to a 4x12 pitch roof and adding 2' eaves, doors and windows, and insulation.
http://www.muellerinc.com/gallery/bu...stom-buildings
The largest standard building they show is 40'x60' for $15k to $19K depending on snow and wind loading. So you would probably be looking at ~$30K for a larger custom design, plus concrete. And concrete ain't cheap. Doesn't cost anything to ask.