I think taking some elements of the TCU build would be the dream scenario and could be done for anywhere from $100-$200 million depending upon what KU is willing to sacrifice.
Phase 1: Trash the East end and build something like the KSU East end and the TCU (west?) end with a better facade. If they are really worried about holding down the cost, they could maybe keep the lower level, build up a facade and boxes behind it. The goal is not to go with a full double deck. Est. Price tag- $40-80MM depending upon the removal of the lower level.

Basically what is pictured above, but without the highest part of the seating scrapped.

Phase 2: This is where the TCU thing comes in to play. Call this thing the HAWK'S NEST. You build suites all along the North End using the Oread stone theme. Square out the horseshoe and build 2-3 party decks that have seating on the stadium side and large out door party decks on the back. "The Hill" stays open and you get a baller elite only building right there facing the tailgating mecca of the sidestreets. Don't mess with trying to link it the football facility, they are separate facilities and you just keep the current football only stuff where it is and focus on fan experience. Trying to re-locate all of the student-athlete stuff is going to kill your budget, you just spent cash on the football only and the all-athlete thing. Save your money and do this thing right.
Est Price Tag: $70-90MM

Basically this ends up being the view from the hill. Mas o menos.
Phase 3: West Side. Here is where the mas o menos comes in to play. Do you want to complete the entire rebuild? By this time the momentum of the baller NEZ suites might have helped roll into a complete demo. But that is a LOT of stuff to move. If it were me, I would suck it up and muddle through with the weird West side, build the band a little platform or something to put them right on top of the visitors or make that the KU end and figure out something else to do with the extra space and have the visitors feeling claustrophobic against the tight sideline.
Est Price tag: $0-$90MM
Conclusion:
Phase 1 & 2 Est cost- $100-180MM
Personally I would rather have the baller NEZ that connects to all the tailgate areas and make it just an enormous party with places for young alums and high rollers both and throw up some facade bandaids on the rest to keep the project on budget. If it is all about the hill, make it all about the hill. Build the NEZ in to one of the best suite/party palaces in the country with the setting behind it. Muddle through the E/W stuff until you can raise the $150-250MM more it would take to do it right.