Cost to enclose Paycor Stadium expected to run $900 million to $1 billion

I said the same thing about the Cleveland Browns Stadium. The cost of doming a structure that size which wasn't originally intended to be a dome is almost as much as building a new stadium

The stadium’s current elliptical shape makes it hard to enclose, Hamilton County Administrator Jeff Aluotto said. And even if such a stadium attracts big events, such as the NCAA Final Four or the Super Bowl, the huge economic impact of those events will not pay for the borrowing needed to construct a dome.

Bingo