Doesn't the cost largely depend on where it's built, too? Like state to state. Isn't that why MetLife was built in NJ? So a direct comparison to stadiums in other states would not be accurate. I have very little knowledge of these matters, though.
The fact that they already own the OP land helps. They should definitely build it there and keep the same game day atmosphere they have now.
Downtown covered stadiums for football? How incredibly boring.