My shop is 30' x 50' with (as you said) 12' walls. I had to do almost $10k of grading (yeah, grading) because I wanted the pad of the shop about twice the size of the shop and because they had to go down about 9' to hit hard pack, and then work their way back up. Oh, and I used existing dirt (removed an unwanted hill in my yard). I have buddies who are contractors (including quite a few who do grading), but I used the guy with 'THE Reputation' for doing excellent work. Also, I don't mix friends and money.
I have 4 50A 220 sockets, plus 220 for the future lift (still debating 2 or 4 post) and 220 for the compressor (out back). I also had to tie in a driveway, put 4' walkways all around, and put a 10' x 12' pad off the back (with walkways) for future 'compressor shed.' I got lights that.....well, as my buddies said when we were drinking beer outside of it Friday night, "Are brighter than friggin daylight." Plus two uber-CFM ceiling fans and 110 everywhere (inside and out).
For plumbing I have a deep sink and a bathroom which (for now) houses only a toilet. Here in good ole CA, anything bigger than 120 sq ft. requires fire sprinklers (as of January 2014). I also added two high pressure outdoor hose bibs for car washing and, if required, firefighting....or at least feeling like I am trying to save my shop.....oh, and probably that 'house' thing. I also had it plumbed for air with drops all over the place, plumbed with pipe, not pvc. Also, the pipes to the outdoor hp bibs are copper, not pvc.
The shop is exactly like my house from the exterior. I had the house built about a year ago and I could not in good conscience put something (literally) in my front yard (I have 3 acres) that did not match the house. So, the roof tiles, hardy board, stucco, and trim all match the house exactly (even the windows).
I'm sure I am missing some stuff, but I am trying to tell the whole story as I know when I was planning this (all 45 years of my life) I read EVERYTHING I could find.
I have not received my final bill yet (I wait with bated breath...) and it will vary due to some last minute additions on my part (having contractor hook up compressor, run CAT 5 so I can hook into my home network, etc). However, I expect total cost including plans, permits, etc to be in the neighborhood of (ready for this.....) $110k. Gotta love CA!
I have land in Texas I bought when stationed there (I am retired military) and I could have built a nice house for that much......it just kills me, but you can't beat the weather and (most important) the wife (RN) has been at the same hospital for 20 years...can't walk away from that! Not to mention I got a pretty solid job when I retired from the Navy.
Happy to answer any questions, I FULLY understand planning a shop. Hell, I spent a month anguishing over whether to go 2 doors or one.........and I drove EVERYONE around me nuts as I planned this thing. My wife is so tired of hearing "shop" that anytime I mention it now she just groans (wait until she sees the total cost.....

) and everyone I work with suddenly 'remembers a meeting'......yeah, I totally get it and will answer any questions/help in any way I can.