Quantified benefits of using FEED/FEL in lieu of 'standard' engineering practice.

Looking for links to free references that have quantified the benefits of using the FEED/FEL project steps (stage gate) in lieu of not doing so.  Is the extra time justified?  If so, by how much?  How much more time is expended in Basic Design with FEED/FEL practices than without?  Assumes a process plant with process options located in the US.  I have seen a un-attributed source that says a 6-23% benefit to both ROI and TIC.  Interesting, but not really helpful.

Also, any metrics (time and cost) that you might know that would show the ratio of FEED/FEL (Basic Desing) to Detailed Design.

Any thoughts appreciated. Thanks,