Shares of Madison Down 9.3%

The Shares of Madison Square Garden Co have fallen their most ever after it disclosed the steep cost of building a new venue in the gambling mecca. The stock fell as much as 9.3% to $266, hitting its lowest mark since January.

Investors were jarred by potential cost overruns of a concert and event venue called the Las Vegas Sphere. MSG approved a preliminary construction budget of $1.2 billion, but a contractor estimated the expense would be $1.7 billion.

Even $1.2 billion would dwarf the budget of other venues. Las Vegas’s T-Mobile Arena, which opened just down the street in 2016, cost $375 million.

MSG plans to open the high-tech Las Vegas venue in 2021. It will host concerts, product launches, award shows and sporting events and feature an interior display the size of three football fields, the company said.