From other posts this seems to be controversial and in this case pretty much outside of any "normal" pricing range. Why would 3 months out be sooo out of line. I frequently book three months out for work and have found as others have stated that early booking leads to higher pricing to be a "urban myth". Has it happened that pricing dropped.... yes certainly. If this is the case when would you call the sweet spot for booking this type of ticket? What would drive UA to put such an insane price on this type of ticket 3 months out? Sorry but I don't get it.
In this case I totally agree that I would have immediately gone to multicity booking through DEN as you and others stated.