If it's a good for local business owners, then let them help pay for it too. Should be an easy sell, based on what you're saying.
If it hosts other events, then somebody is making money off that, so let them chip in too.
If it will provide additional tax revenue for the city, then they should put a provision in the bill that all the tax dollars will be reimbursed back. Or they should take out a loan based on the projected additional tax revenue.
They won't do any of these things, though, because nothing is as rosy as you say it is.
Has anyone put together a massive projection of financial and economic benefits for the city, based on what you're saying? Something that will specifically describe how say an average hourly worker for these business will benefit? I doubt it, because there's nothing.