Actually, it does cost the taxpayers. That property, waterfront property, doesn't pay any taxes because it is government owned. And the hotel prices are now higher than they should be to pay for the "tourism tax" you mentioned. And the "tourism tax" could have been used to promote the area which would have brought more business to the people here who do pay taxes so they lose revenue because of a convention center that will always lose money.
And the proposed hotel, the fourth attempt, will also compete with hotels that receive no subsidies. Not a good deal for taxpayers, but then again, it wasn't the taxpayers that convention center advocates really care about.
As for the wedding, taxpayers helped fund it, otherwise, the building wouldn't be affordable to rent.