I am having a 50x50x14 with three 12' doors built right now. They poured the slab last week. Our dimensions are different but we are within 100 sq ft of each other.
Figure about $9000 on the concrete. This is a good slab with footings with rebar and wire mesh in the main part. It also includes an approach to get into the shop. Concrete around here goes for $3.50 a foot if you want someone that does a good job.
Labor you are probably looking at about 5k. Insulation is extra and will run about 6k for a building that size. Wiring I do not know as I have not got there yet but will be doing that my self.
My building is being built for 37k turnkey which includes dirtwork, slab, materials, one 3x7 door, 3 12x12 insulated doors, and 1" spray foam insulation. Electrical is extra. I might add I shopped it around pretty hard and compared prices from 4 contractors. I did get one quote that was about $800 less but the contractor had bad reviews from the BBB.