What do the letters mean in my numbers?
They're si unit prefixes: Number Suffixes
Why are the buildings so random cost efficient? My Oil Sands costs more than 50x Saudi Field :(
The rate of increase is variable because different investments have different economies of scale. For the early part of the game, the initial cost of a property is the most important, but later the multiplier becomes most important. The multipliers are listed here: Level Cost Increases