Construction costs in 2008 hit all time highs but luckily have pulled back down since then. This is because of simple supply and demand. When the real estate boom was still in full swing, the cost of construction materials was high because of the high level of demand for these things.
However now that demand has slowed and supply is still high prices are reducing. This puts rules of thumb out of the whack when using them to estimate.
This means professionals need to step back and estimate with a greater level of accuracy then before.
One way to do this is to adopt PlanSwift construction takeoff and estimating software. This program allows you to estimate construction cost with a high level of accuracy and the ability to update construction costs numbers as prices continue to vary over time.