OK, I think I can give you some info that might make you feel better than reading about all those people who paid way less on their concrete. I'm paying a truckload and I'm in a rural area of Ohio, I look out my front windows and see the neighbors cows... I'm in the process of building now, they will be pouring the walls tomorrow.
My building is bigger at 40X64 but so are the bills. Like you I am building on a slope which is 95% the reason for the crazy costs.
With footers, walls, 6" concrete floor, labor, drainage and back fill it's costing me $70,000. That includes 140 yards of concrete and 4 tons of rebar. An entire building with concrete floor that size on level ground would cost less in my area. I couldn't cut a huge swale behind the garage and level it out because 10 feet behind it was a buried high voltage power line.
My back wall is 10' high with 2' down to the footer and the front wall is 6' high with 2' down to the footer. They originally were only going to put 2' above ground but I thought that would look dumb and changed it to 4' so that it would look like wainscoating. Picture this, you walk into the garage at grade in the front, when you get to the back the floor is 7.5' below grade.
The footers are all 14" thick, in the front they are 3' wide and in the back they are 4'3" wide.
For those with buildings on flat ground I am envious. This wall is not overkill, it is not a "foundation wall" it is a "retaining wall" meaning it doesn't have a house floor tying the front and rear walls together preventing the walls from caving in. The walls are all 10" thick. The building itself sits on the concrete is going to be a pole building with metal siding, metal roof, and metal clear span trusses. After all the concrete expense, I'm thinking I should have went stick built...
I'm thinking of starting my own build thread to help others realize the costs and to discourage building into a hill. Might have been cheaper to buy some flat property...
Hope this makes you feel better.
Brian