Im trying to get a shop built pretty quick after the wife and i finish the house we are currently building so im up to speed on stuff, at least down here in Texas. I cant imagine pricing is THAT much different in other parts of the country. Im leaning towards pole barn because its way cheaper than steel and I cant be convinced that its a lesser building.
My only plan beyond the building and concrete is electrical to the shop and im setting the house up to be easy to pull from the 2nd panel(getting 400a service on the house) and get a trencher to run out to the shop. I'll do all the internal wiring and my master electrician buddy will pull the permit and do final connections for everything which will save me some money. Going to run fiber optic at the same time and maybe a water line.
Im not planning on running any plumbing to the shop outside of MAYBE a water line and an outside spigot as the price for that was stupid when I asked my buddy who is a plumber... He quoted me 6k to rough in a half bath... said hooking to the septic and pulling water from the house is the main driver. That was him doing 100% of the work including trenching... he said if I trench on his plan, that will cut down maybe 1500-2000 since he would have a full day in trenching then filling the trench back in. Still 4k is a lot for a rough in... I can walk 150ft to the house to piss.
Spray foam will likely run my 8-10k bucks for the whole building. If I do only the under side of the roof, likely 4k. With a pole barn with 6x6 posts you can frame it out with 2x6 in 24" centers, throw batt insulation in for way less than spray foam, then finish drywall. Insides of red steel beam buildings are a little harder to finish out for a nice look(if thats what you are going for).
I cant talk about in slab heat as I am not interested in that. But for you up in ID, I would look hard at that plus a boiler. Probably the cheapest way you will heat that building. Down here I am more concerned about A/C and will likely do a small mini split system. The Mr. Cool DIY systems have good reviews over on Garage Journal. They are also wifi connected so you can run them from the main house. You should also be able to get a wifi thermostat for a boiler for in floor heat.
The more you can do the cheaper obviously. I would LOVE to be able to do my own concrete, but ive never worked concrete before and I dont want to learn on a 40x40 slab... I MAY do the dirt work as I am planning on picking up a JD X758 with a 3 point hitch so I can get a box blade(and other implements). It might take me awhile to do site prep, but if its free, fuck it.