I think the basketball arena can be renovated or rebuilt for way under $150 million. Loyola's Joe Gentille Basketball Arena was done (maybe went through significant renovations) for less than $10 million in 2011. What is Illinois paying for its renovations right now? I don't think it is $150 million. A basketball arena is a lot less expensive than building a football stadium.
As for comparing the state of the football program versus the basketball program, I do not think the football program is way ahead of the basketball program in light of the past two football seasons of 5-7 records and no bowl games. This year for football does not look promising as NU appears to be starting a redshirt frosh QB, key WRs getting injured (Christian Jones) and our WRs are weak to begin with, a reconstructed offensive line with a number of positions wide open with no clear starters, a poor set of defensive tackles and a lot of key defensive players graduating in Ibrahim Campbell, Chi Chi Ariguzo and Jimmy Hall. Unfortunately, I think another non-bowl season is a distinct possibility.
Back to facilities, yes, it needs to happen with basketball eventually. But schools have succeeded without amazing facilities. There once was a school who became the most powerful team in the nation without amazing facilities. I could be talking about Coach K and Duke, but I am referring to John Wooden and UCLA who won a number of national titles before Pauley Pavilion was built.