What did the 2500 in the family room include?
I also don't understand what you mean by Insteon has the same stuff. Insteaon, as far as I can tell, makes dimmers and switches. Everything else from their own site is third party equipment. You say that Insteon has "everything" except good software or remotes. I would say that good software is the most important thing to have.
If you have a large home and you were quoted 115k for a complete automation system, including lighitng control, audio, video, security, hvac, touchscreens then I would say that isn't out of line at all. I would still say that that is beyond what C4 is aiming at, but it doesn't seem completely out of touch either.
If you are going to cobble together a bunch of various systems into a DIY solution, then you can probably do it cheaper. If you eliminate all of the labor you are paying for in the 115k quote, what is the real difference? I know Insteon dimmers are only 40 bucks, so you will have some savings there. Where else?