Building a garage, cost $$$$

I have a metal shop for my business.
I know there are folks from all over the country posting here but I think is is prudent to bring this up.
It is hotter than Hell in the summer and you'll freeze your butt off in winter....IF you don't insulate the thing as thick as you can. Even then it may be uncomfortable on extreme temperatuire days. Yesterday it was 104 here in Sacramento and in the winter it can get into the upper 20's at nite.
This can add LATER to your cost when you discover this after the fact, so you should figure that cost in now.