There is nothing wrong with new stadiums and arenas per se — well, unless you think they’re ugly, but plenty of old ones are, too. But the reason the U.S. has so many of them, and is tearing down its not-quite-as-new ones to replace them with shinier models as fast as possible, has nothing to do with the alleged riches that can be made off of them, and everything to do with the fact that in order to get those fat checks from the public treasury, you need to be able to present a giant construction bill as justification. If we could only start subsidizing something useful instead ... there would still be a massive transfer of money from the public to a bunch of rich dudes, but at least we might get something out of the bargain other than fancier cupholders.
So, the numbers for construction are already juiced when the proposals are made. Then the municipal wizards come along afterwards and say, "Uh-oh. We did not expect archaic utility lines because you know they are underground and we can't see them yet even though it was like 1969 since the last time everything was dug up here at Sulphur Dell, and we could logically deduce the odds." So, they tack on millions more. I shouldn't lose sight of the original sin to the ineptitude of the bean counters.