Cost Analysis and Performance of Engineered I-Joists

[offthegridcortland]

Has anyone ever done a cost analysis of using engineered I-joists for the 20' wide spans versus dimensional lumber?  I know the dimensional lumber would probably be cheaper, but if you were going to change the plan's layout to keep the bottom floor more or less completely open, you would need a a beam of some size as well as posts.  Those contribute to the overall cost.  I personally like the look of the exposed beam, but the supporting posts over a 34' run are a serious consideration when trying to create an open floor plan.  I'm also curious as to people's perspective for the I-joist's performance under foot. Thanks, Aaron