It used to be you could build for $100/sqft on flat land and about $200-300/sqft on a slope...but inflation and also skyrocketing prices in the Bay Area have doubled/tripled that. 

We finally sold the house in 2014 right before the value skyrocketed here in Thornton, CO.

I've also noticed the earnest money requests for REO's have skyrocketed.  

Or can it truly skyrocket as deemed necessary from county to county?

Some landlords tried including electric, gas, cable, internet with the rent to the students... students loved it, landlords got clobbered, because students were now leaving all the lights on, their windows open in the winter with the heat on, etc and the electric/gas bills skyrocketed which now the landlord was paying.  

Long story short, Hurricane Katrina caused materials to skyrocket, we ran out of construction money and used our own, the project ran long and pre-sale buyers bailed.  

She was pushed into Oakland because Walnut Creek rent skyrocket!

Rents there even for one bedrooms have skyrocketed.  

Prices in Logan Square,  Avondale areas have really skyrocketed recently.  

The prices are skyrocketing with all of the foreign investment.